Quest Volume 26, No. 1 February 2025

The Journal of Global Underwater Explorers

Quest

CCR FUNDAMENTALS

Redefining entry-level rebreather training

THE UB-88 PROJECT

Ghost Diving USA restores history and ecosystems

HALCYON SYMBIOS

Are chestmount units the future of CCR diving?

SAVING THE CRAYFISH

Project Baseline divers locate and track populations

ACCIDENT ANALYSIS

Cave diving risks are identifiable and manageable

EDITOR’S LETTER

GUE CCR

GUE’s preference for simplicity and standardization has historically delayed its adoption of new technologies. The fully closed rebreather gained traction in the sport diving community during the early nineties with the introduction of the AP Valves Inspiration and other units. However, for several years, GUE divers harbored skepticism towards electronics, oxygen cells, and decompression computers. This skepticism was justified, as the technology was still in its infancy, and the early adopters of the first generations of sport diving CCRs faced several severe accidents.

It wasn’t until 2013 that GUE launched its first CCR program, marking its embrace of rebreather technology. With significant advancements in safety and reliability, GUE developed a comprehensive training program to ensure CCRs were not only safe but also valuable tools for advanced exploration and expeditions.

The first generation of GUE CCR students came from the top tier, with GUE Tech 2 as a prerequisite. This provided instructors with highly skilled candidates, reflecting GUE’s conservative approach—unlike other agencies that offered CCR training to far less experienced divers with minimal prerequisites.

But as you can read in Graham Blackmore’s article on page 32 in this issue of Quest, GUE is now offering CCR training to Fundamentals students with tech passes. This allows them to bypass the open-circuit Tech 1 class, which has been the prerequisite certification since 2018. Helium prices and availability have made it increasingly unreasonable to require Tech 1 for a diver who wants to pursue the closed-circuit route directly.

Another aspect that will broaden the choices of CCRs is the recent introduction of Halcyon’s Symbios chestmount rebreather. Although its exact integration into the GUE ecosystem is still uncertain at the point of writing, it is highly likely that we will see another closed-circuit rebreather endorsed alongside the reliable JJ-CCR before the end of 2025. For more information, read John Kendall’s article on the Symbios on page 52, and Dimitris Fifis’ feature describing the pros and cons of chestmount units on page 62.

The robust nature of the JJ-CCR is exemplified by the California Ghost Divers team and their cleanup project on the UB-88 submarine. Refer to page 12 to learn more about how the JJ-CCRs were utilized in the successful project.

GUE’s CCR training continues to evolve, balancing safety, standardization, and exploration. With expanded access and new rebreather options on the horizon, divers have more pathways to integrate CCRs in their training and exploration.

Jesper Kjøller Editor-in-Chief jk@gue.com

Quest

Editor-in-chief

// Jesper Kjøller

Editorial panel

// Michael Menduno

// Amanda White

Design and layout

// Jesper Kjøller

Copy editing

// Pat Jablonski

// Kady Smith

Writers

// Kirill Egorov

// Daniel Riordan

// Dorota Czerny

// Ulrik Juul Christensen

// GÖzde Akbayir

// Jim Babor

// Robert Corby

// Martin Maple

// Graham Blackmore

// John Kendall

// Dimitris Fifis

// Fred Devos

// Todd Kincaid

// Chris Le Maillot

// Jarrod Jablonski

Photographers

// Kirill Egorov

//Jesper Kjøller

// Bori Bennett

// Angie Biggs

// Tianyi Lu

// Kian Farin

// Robert Corby

// Martin Maple

// Mike Cross

// Mike Waddington

//Julian Mühlenhaus

// Derk Remmers

// Stefan Panis

// Petr Polach

IN THIS ISSUE

6

12

HQ CORNER // MASTERY LEARNING

After years of development, GUE has launched an adaptive online platform for the Fundamentals and Performance Diver programs to offer personalized learning beyond standard online materials.

THE UB-88 CLEANUP PROJECT

The UB-88, a WWI German submarine, lies off California’s coast as the only known German U-boat on the U.S. West Coast. In December 2024, Ghost Diving USA volunteers spent five days removing ghost nets and promoting marine conservation at the site.

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PROJECT BASELINE // SAVE THE CRAYFISH

White-clawed crayfish are threatened by invasive North American crayfish. Conservationists use “ark sites” to protect them, and divers monitor populations via citizen science. The Midland Pools Project uses former quarries as conservation sites, offering hope for the crayfish.

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CCR FUNDAMENTALS – NEW PATH

GUE’s new CCR Fundamentals course offers a streamlined path for open-circuit divers transitioning to rebreathers. The program focuses on core skills and prepares divers for deeper technical diving.

46

PORTFOLIO // STEFAN PANIS

The Belgian diver and photographer started young, transitioning from film to digital in 2012. A technical CCR diver, he’s documented dives worldwide, focusing on Belgian mines and Dover Straits shipwrecks.

52

HALCYON SYMBIOS CHESTMOUNT CCR

Halcyon’s Symbios CCR is poised to revolutionize rebreather diving. This compact, chestmounted unit features cutting-edge wireless technology, a lightweight design, and adaptability for all divers, from recreational to technical.

62 74

CHESTMOUNT CCR’S // PROS & CONS

Chestmounted rebreathers offer advantages in size and accessibility, making them a compelling alternative to back-mounted systems.

CAVE DIVING // ACCIDENT ANALYSIS

Caves inspire both curiosity and fear, and cave diving is often viewed with apprehension. While past fatalities have contributed to this stigma, the risks of cave diving are identifiable, predictable, and manageable.

HQ CORNER

A bold leap into next-generation

After several years of development, GUE has released GUE Mastery Learning™—the first iteration of its online learning platform with modules for the Fundamentals and Performance Diver. The platform offers much more than mere online material. With GUE Mastery Learning™, GUE has entered a new dimension of personalized and adaptive learning opportunities for its trainees. It is our privilege to introduce you to GUE Mastery Learning™, which is powered by the Area9 Rhapsode Capable™ suite of technologies.

Underlying GUE Mastery Learning™ is Area9 Rhapsode Capable™—the world’s first multi-dimensional adaptive learning platform. It is cloud-based, with responsive design (i.e., works on all platforms and screen sizes), and it is heavily leveraging many different types of artificial intelligence, robotics and analytics. While technologically cutting-edge, it is built on the simple premise that a learning platform should start with the learner, giving everyone the opportunity to maximize their potential to grow and be productive. Using the latest in learning science, powerful artificial intelligence, and an intuitive user interface, Area9 Rhapsode™ provides all the capabilities needed to deliver optimal learning outcomes and retention as well as drive behavior change. So

far, Area9’s adaptive and personalized technologies have been used by dozens of millions of learners in schools, universities and corporations in more than 185 countries for everything from anatomy to financial compliance. Leveraging the power of Area9 Rhapsode Capable™, GUE has been able to develop modern education for the scuba diving industry and, with it, to bring our organization to the absolute forefront of education.

Area9 Rhapsode™ is based on a four-dimensional education framework. This framework focuses on creating a multifaceted, mastery-based approach to learning that emphasises the cognitive and psychological skills needed to manage complex diving and exploration safely. These four dimensions are knowledge, skills, character, and meta-learning. What do those dimensions mean for GUE-trained divers and GUE trainees?

next-generation of GUE education

Unlike most platforms, Rhapsode prioritizes selfreflection and assessment, dynamically adjusting emphasis, remediation, and redundancy to create individualized learning paths.

KNOWLEDGE Divers at all levels must develop a deep understanding of the science and mechanics of diving. The “why” behind each concept is crucial to understanding and galvanizing the critical components that influence a diver’s decision-making underwater.

SKILLS Divers must master basic diving skills, including precision trim and buoyancy control, multiple kicks, stability, and control. They must also develop keen problem-solving skills specific to complex or even emergency scenarios, meticulous planning and communication skills, team dynamics, situational awareness, and risk assessment skills.

CHARACTER More advanced diving requires resilience, self-discipline, and poise under pressure. Character traits like accountability, patience, hon-

esty, and humility (i.e., acknowledging the limits of personal skill and environmental challenges) are essential, as they help divers approach dives with a responsible attitude. Perseverance, fairness, and ethical responsibility ensure divers respect environmental conservation as well as the safety and well-being of other divers. It is critical that GUE fosters a safety-oriented culture. The “gradient” here is 80/20: 80% Character/20% Skills is what will make GUE divers uniquely competent.

META-LEARNING Divers must learn to understand and reflect on personal progression, limitations, and responses to stress. Meta-learning involves developing self-awareness about one’s physical and mental responses to diving conditions. It allows divers to manage fear, stay focused, and adjust to unexpected events underwater.

Personalization

The secret to Rhapsode’s success and, thus, that of GUE Mastery Learning™ is personalization. Rhapsode uses many factors, such as progressive measures of proficiency, confidence, time, and self-awareness, to accurately measure each learner’s weak and strong areas and identify any misconceptions they may hold. Rather than simply presenting learning content, as almost all other platforms do, Rhapsode extensively uses self-reflection and self-assessments. In real-time, it determines where to put more emphasis, where to remediate, and where to save time by avoiding redundant content the learner already knows. Resulting learning experiences are unique to each learner and determined automatically despite using the same underlying content. Everyone will go from A to B, but how they get there is different and individualized.

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progress, estimated time to completion, most challenging learning objectives, and metacognitive skills (actual knowledge vs. perceived knowledge). This instant feedback enables learners, teachers, and subject matter experts (SMEs) who build the content to understand better where they should focus their efforts.

The journey

As access to GUE Mastery Learning™ is granted to trainees while enrolled in GUE courses, each can return to the platform and refresh their knowledge at any time.

GUE Mastery Learning™ is based on the concept of the flipped classroom: it reverses traditional teaching such that trainees learn foundational content at home at their own pace. As it works on all types of devices, the trainee can complete GUE coursework any time, anywhere the internet is available.

The platform approaches learning more smartly and intelligently: it enables trainees to learn and retain information more efficiently and effectively while providing a detailed overview of learners’ knowledge and knowledge gaps. Doing so makes the learning experience far more efficient; it becomes a powerful addition to other learning methods because it serves as an “always available tutor,” providing the right information at the right time, including refreshing learning to “make it stick.”

The platform offers in-depth learning analytics that include a detailed outline of learning

FACT FILE // WHY AREA9?

GUE has three main goals in adopting the flipped classroom learning architecture: Trainees will enjoy more hands-on and in-water time with GUE instructors. This creates access to more in-class dive opportunities. Our courses historically evolved from the need for in-water performance, confidence, and comfort. We always strived to extend in-water time versus lectures, which, in the past, was very challenging due to the amount of knowledge that needed to be conveyed to each trainee. With the adaptive principles behind GUE Mastery Learning™, trainees can take all the time needed to learn the theory. Instructors can avoid late evening, long lectures and allow trainees to absorb basic content at their own

Area9 is located in the prefrontal lobe of our brain and is involved in short-term memory, evaluating recency, overriding automatic responses, verbal fluency, error detection, auditory verbal attention, inferring the intention of others, inferring deduction from the spatial imager, inductive reasoning, attributing intention, sustained attention involved in counting a series of auditory stimuli. Smply said it’s for learning and adaptation to new situations and interactions.

Strengthen learning by focusing on the instructor’s dive and exploration experience, using class time for discussions, knowledge application, and hands-on training.

pace. Trainees will understand and retain more than traditional lecturing (which is limited by a predominant one-directional information flow). Students will learn during the course more quickly, as they will arrive prepared. This preparation is not merely theoretical; rather, trainees will have an understanding of what they should expect, which will reduce common sentiments of intimidation and anxiety. Trainees will feel more engaged from the start of the course.

Naturally, this will challenge instructors to answer educated questions early in the course, “connect the dots,” and lead the trainees towards critical “a-ha” moments. This allows trainees to have emotionally intense experiences, which will prepare them for their future diving endeavors.

Adaptive learning will facilitate deeper foundational understanding and maintenance of relevant knowledge. As access to GUE Mastery Learning™ is granted to trainees while enrolled in GUE courses, each can return to the platform and refresh their knowledge at any time. As divers progress through GUE training, they will

not need to listen to the same lecture in each class. They will test retention and understanding of previously attained knowledge and add new concepts associated with their course. For example, if a student signs up for the a Cave 1 class, they will review the gas management module from the Fundamentals program in the form of an individualized refresher test, which will be based on their performance history in this module during the Fundamentals course (and actually in any other GUE course the student has completed on the platform). Based on this, the platform will start adding relevant cave gas management content and test for its comprehension. In the end, the student will not only learn new things but refresh their basics, too. This, again, will shorten the time spent on the theoretical part and allow divers to be involved in learning diving while diving.

Grit

We can drive the development of grit through an even stronger focus on the instructor as the source of inspiration by providing a personal

PHOTO BORI BENNETT

FACT FILE // NO EXAMS

One of the most prominent changes to the programs is that the final theory exams are gone. The new mastery learning architecture monitors the development of competencies at very high resolution and granularity as the learning decays over time. The high-frequency formative assessment allows for elimination of the written tests, as the written tests as the learners are continuously assessed, but with the primary goal of aiding the learning process. In this model, you can only fail if you quit. There are only two grades: top grade… or incomplete!

context from the instructor’s diving and exploration career and activities. In-class time with a GUE instructor should be dedicated to applying knowledge through discussions in the context of the instructor’s extensive dive experience, practical skills, and dive training ahead. This model encourages active learning and allows instructors to provide more personalized guidance and support during class. It shifts the focus from passive content delivery (informing) to fostering more profound understanding and practical application (inspiring). By preparing for the in-person time with the instructor, students arrive ready to engage and discuss, making in-person time more interactive and impactful–and getting to the skills and character (leadership, resilience, situational awareness, curiosity, etc.) development much sooner.

Deliberate practice

The transpiring concept throughout each of these innovative learning principles is “deliberate practice.” See Anders Ericsson: PEAK – How to Master Almost Anything , 2016. Deliberate practice is a highly structured and intentional practice aimed at improving performance in a specific skill or area. Unlike general practice, which may involve repeating an activity, deliberate practice involves focused efforts on tasks beyond one’s current abilities, with immediate feedback and adjustments for improvement.

Deliberate practice requires effort and consistency and often involves pushing oneself out of a comfort zone to tackle difficult aspects of a skill. This approach is commonly seen in fields like sports, music, and other top-performers such as physicians or special forces but applies to any area where high-level proficiency is desired.

Deliberate practice has four principal characteristics:

Clear goals are specific but challenging. They target areas for improvement rather than merely repeating what’s already known. Students have to understand not just what to practice but why they must practice it.

Focused attention means practice with minimal distractions to maximize learning and retention. This is provided not only by a well-chosen underwater classroom but also by the freedom to learn in a collaborative, not strictly competitive, environment.

“Theory discussions are still important, but they should be much shorter, more focused, and centred on practical application, dive planning, and the context relevant to the instructors’ experience as more advanced divers and explorers.

Immediate feedback, either from an instructor or through self-assessment, is needed to identify mistakes and refine techniques promptly. In the water, this refers to active teaching when the instructor provides immediate feedback and confirmation of progress while underwater and allows students to implement the feedback

straight away. Of course, the post-dive feedback sessions on the surface are essential, but the impact of active underwater teaching is invaluable.

Reflection and adjustment means analyzing performance to refine skills, allowing for continuous improvement over time. This occurs through video debriefings during class, postdive and post-class debriefings, and teaching self-evaluation. It rests on the promotion of teamwork for self and team improvement. This is critical not only for courses but for any form of more advanced activities like exploration diving or project diving, as humility, open-mindedness and learning from one’s own and team’s struggles and mistakes will make a definite impact on both success and safety.

The long-term goal is to eliminate all lectures in which the instructor presents a pre-made presentation. Theory discussions are still important, but they should be much shorter, more focused, and centred on practical application, dive planning, and the context relevant to the instructors’ experience as more advanced divers and explorers. Now, the instructor’s personal dive experience, project participation, exploration, diverse environments and teams are critical to becoming the inspirational educator, guide, coach and mentor we aim for.

With this new, powerful tool, GUE is striving to educate a new generation of divers, instructors, explorers, and leaders of the industry whose goal will be continuous development, improvement, and growth. 

Ulrik Juul Christensen is a Danish entrepreneur, educator, avid scuba diver, CCR diver, underwater photographer, and instructor. He is the CEO of Area9 Lyceum, which has been pioneering personalized learning platforms that use adaptive technology to shape learning to individual learners. With his background as a medical doctor, he has spent three decades in human

factors, simulation, and debriefing research as well as high impact/ high stakes learning. More than 50 million learners from middle school to physicians have been using Area9’s platforms. Christensen serves on the boards of several companies and organizations, including the Technical University of Denmark (DTU) and GUE.

www.masterydiving.com

Dorota Czerny is a highly experienced diver who fell in love with the ocean in 1996. She transitioned from teaching at a university to teaching scuba diving due to her passion for the sport. As Vice President of Global Underwater Explorers, she is highly skilled in technical, cave, and rebreather diving, and is dedicated to developing the organization’s

educational component. Her focus is on creating a new generation of explorers and young scientists with GUE’s NextGen Scholarship program. Dorota’s dedication to diving education extends beyond her work with GUE as she actively explores caves and wrecks around the world.

Ulrik Juul Christensen

Dorota Czerny

RESTORING HISTORY &

ECOSYSTEMS

PHOTO TIANYI LU

Curtis and Jim work to cut the net free of the stern torpedo tube.

– THE UB-88 CLEANUP PROJECT

The UB-88, a World War I German Type UB III submarine, rests quietly on the ocean floor off the California coast, bearing witness to over a century of history. Surrendered to the United States on November 26, 1918, the submarine traveled across the Atlantic and through the Panama Canal before being intentionally sunk during naval exercises on January 3, 1921. Today, it lies approximately 12 km/7.5 mi south of San Pedro, California, at a depth of about 58 m/190 feet. As the only known German U-boat on the U.S. West Coast, the UB-88 serves as both a historical wreck and an artificial reef. In 2024, this remarkable wreck became the focus of a major environmental cleanup effort aimed at removing ghost fishing nets, which endangered marine species and obscured the site. Over five intensive days in December 2024, Ghost Diving USA volunteers worked to restore this underwater landmark, remove hazardous material, and promote marine conservation.

CAVE DIVING

Angie, Juan, Shane, and Daniel with the 700 kg/1500 lb section of net recovered on day three.

PHOTO ANGIE BIGGS

The groundwork for the UB-88 cleanup project started months earlier, in January 2024, with a series of survey dives that laid the foundation. These dives were crucial for assessing the wreck’s condition and understanding the extent of the ghost net problem. During the first dive on January 24, the team captured thousands of images to document the site in detail and to begin the process of making a photogrammetry model of the wreck. Further dives in February and April built on this work, refining the data and completing a thorough visual survey. Divers carefully mapped the wreck, noting how nets were tangled within its structure and buried in the surrounding sand. These efforts provided the team with a clear understanding of the challenges ahead and formed the basis for planning the December cleanup operation.

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Building the right team was just as important as securing resources. A dedicated 12-person dive team was assembled, including technical open-circuit and JJ-CCR rebreather divers, along with five safety divers.

Planning and preparations

Preparation for the UB-88 cleanup project took months of planning and logistical coordination. With the operation scheduled for December 16-20, securing the necessary resources and assembling a capable team was a top priority. Two vessels, the Giant Stride and the Bottom Scratcher, captained by Jim Simmerman and Kevin Bell, respectively, were secured to serve as the project’s base of operations.

Funding and support came from a diverse group of sponsors and collaborators, including Healthy Seas and Hyundai Motor America. Healthy Seas, a foundation dedicated to addressing the issue of marine litter, particularly fishing nets, works to promote healthier seas and repurpose waste into innovative products through collaboration with partners. Hyundai Motor America’s involvement as a main sponsor underscored their commitment to environmental sustainability and marine conservation. Their contributions, along with numerous grants and private donations, made this cleanup project possible. Building the right team was just as important as securing resources. A dedicated 12-person dive team was assembled, including technical open-circuit and JJ-CCR rebreather divers, along with five safety divers. They were supported by a nine-member surface team that handled essential logistics. Jamie Mitchell from Zen Dive Co. ensured a steady supply of tanks and gas, while the surface operations ran smoothly thanks to a collective effort from everyone involved.

As part of the preparation, the photogrammetry model created earlier in the year played a crucial role. It was used to produce a 3D-printed model of the site and the wreck, which helped the team plan every aspect of the cleanup. The model was also utilized during briefings to visualize the wreck’s structure and the placement of ghost nets. Beyond its practical use, the model serves as a powerful outreach tool, bringing the

Norbert and Jung work to free a section of net.

underwater world of UB-88 to life for a wider audience.

With the logistics in place, a strong team ready, and a clear action plan, the stage was set for the UB-88 cleanup operation.

Staging and documentation

The operation kicked off early on December 16, with the team setting off on a 90-minute journey to the UB-88 wreck site. Ghost Diving USA CEO and President Jim Babor led a detailed briefing to outline the day’s objectives. To help orient team members less familiar with the site, the 3D-printed model created from earlier photogrammetry work played a pivotal role in pre-dive briefings. The focus for Day 1 was twofold: staging equipment for the upcoming net removal dives and initiating a substrate study, led by Norbert Lee, to evaluate the ecological impact of ghost nets on the submarine wreck.

During their 35-minute bottom time, the divers captured critical baseline photographs to document the wreck’s pre-cleanup condition. Divers used a custom hang bar for secure decompression stops in the open water of the busy shipping channel.

Full-scale net removal

Day 2 kicked off with the team diving into fullscale net removal. To avoid overcrowding in the tight underwater space, the teams worked in shifts.

Team 1 started by carefully moving fragile marine life, like Metridiums , out of the work area. They then attached lift bags to sections of the nets to prepare for removal. Team 2 focused on clearing the nets from the port and starboard sides, with David making a special effort to free fish and crabs trapped in the debris. Team 3 worked on cutting the lower sections of the net.

PHOTO KIAN FARIN

FACT FILE // HISTORY OF UB-88

UB-88, a German submarine from World War I, was built in 1917 and commissioned in 1918. Armed with torpedo tubes and a deck gun, she was designed for stealth and assigned to the I U-Flotille Flandern based in Zeebrugge, Belgium. During her active service, UB-88 sank several Allied vessels, including the British steamer Princess Maud and the Swedish Dora. Despite facing intense counterattacks, UB-88 successfully completed her missions.

After Germany's surrender in 1918, UB-88 was handed over to the U.S. as part of a Victory Bond drive and to study German submarine technology. She toured U.S. ports to promote war bonds before being decommissioned in 1920 and scuttled in 1921.

Rediscovered in 2003 near Long Beach, California, UB-88’s wreck has since become an important historical and archaeological site, offering insights into World War I submarine warfare.

The German WWI submarine UB-88 sank several Allied ships before being surrendered in 1918. Used in U.S. Victory Bond tours, it was scuttled in 1921.

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Day 2 kicked off with the team diving into full-scale net removal. To avoid overcrowding in the tight underwater space, the teams worked in shifts.

A section of net, showcasing the challenging conditions divers faced, as Jim prepares the bottom section for lift bags.

FACT FILE // SCIENTIFIC STUDY

Abandoned, lost, or discarded fishing gear (ALDFG), also known as ghost nets, can cause significant harm to marine environments. These nets result in unintentional fishing (when marine life becomes trapped), ingestion of microplastics by wildlife, smothering of benthic organisms, and surface damage from the nets moving in the water. In Southern California, where Ghost Diving USA operates, strong tidal currents contribute to the movement of ghost nets, which scrape against shipwrecks and ocean floors, causing further ecological harm and disrupting the habitat of benthic communities.

The UB-88 Cleanup Project aimed to evaluate the impact of removing ghost nets and whether doing so could help restore habitats by allowing new life to settle on surfaces previously affected by the nets. The goal was to see if removing the nets from the torpedo tube and other areas would support ecological recovery by creating space for marine life to return.

During the UB-88 cleanup, the team focused on a ghost net located on the submarine’s aft torpedo tube. This net, suspended by a float, was frequently moved by currents, causing abrasion on the tube’s surface. This presented a valuable opportunity to compare affected areas with those not impacted by the nets, offering insights into how ghost nets damage surfaces and whether removal could encourage recovery.

The UB-88 Cleanup Project aimed to monitor changes at the wreck site while minimizing disturbance. Before removing the ghost nets, the team marked their original positions. A visible line was then installed across the torpedo tube to serve as a reference, with stations set at intervals using numbered markers, or “cookies.” The team set up five stations in areas impacted by the ghost nets and five in unaffected areas.

To track changes, the team used 0.5 x 0.5-meter photo quadrats to capture images

TEXT NORBERT LEE

of invertebrates and assess the coverage of colonial invertebrates in each area. These images were critical in documenting the condition of the site before and after net removal.

While the study provided valuable insights, it was limited by the small area affected by the nets, as well as the challenges of working at a depth of nearly 61 m/200 ft. To better understand the long-term effects, the team plans to return periodically, if funding allows, to continue monitoring changes. This ongoing research could form the foundation for a more extensive marine conservation project, providing important data on how ecosystems recover after ghost net removal and informing future efforts to clear marine debris.

References

• Gilman, Eric, et al. “Introduction to the marine policy special issue on abandoned, lost and discarded fishing gear: Causes, magnitude, impacts, mitigation methods and priorities for monitoring and evidenceinformed management.” Marine Policy, vol. 155, Sept. 2023, p. 105738, https://doi. org/10.1016/j.marpol.2023.105738.

• Macfadyen, Graeme, Huntington, Tim, and Cappell, Rod. (2009). Abandoned, Lost or Otherwise Discarded Fishing Gear. UNEP Regional Seas Reports and Studies. 185.

PHOTO KIAN FARIN

Angie checks on surfacing divers.

The highlight of the day was successfully removing a 225 kg/500 Ib section of fishing net. The Giant Stride, serving as a chase boat, recovered the net once it surfaced, while safety divers helped keep everything running smoothly underwater by checking on the working divers at their 21 m/70 ft and 6 m/20 ft decompression stops and taking extra equipment from the working divers as needed. This marked the first big milestone of the cleanup, with the team’s coordination and teamwork really standing out.

Record-breaking haul

The team faced one of their toughest challenges on Day 3: removing the largest entangled net on the UB-88 and clearing the torpedo tube. During their dives, the teams tackled a massive 680 kg/1,500 Ib fishing net—marking the largest single haul in the team’s history. The size and weight of the net turned this achievement into a true test of teamwork. To coordinate this day of diving the first team descended to stage final lift bags on the massive amount of net. Thirty minutes later the cutting team, which con-

Lift bags staged and ready on the bottom section of net.

sisted of Karim, Curtis, and Jim descended and started cutting for their planned bottom time of 35 minutes.

Despite the effort and complexity, the results were worth it. By the end of the day, the wreck was completely free of ghost nets. The remaining net now lay on the sand, beneath the stern of the wreck.

Remaining hazards

Day 4 shifted the focus from large-scale net removal to addressing remaining hazards and documenting the environmental impact. Some nets still posed a risk due to their buoyancy in the sand, creating potential entanglement hazards for marine life. The divers carefully gathered these remnants into one area and secured them with lift bags for easier removal later. The teams also secured sections of net rope cinches to bundle large sections, attaching lift bags with the plan to return on the final day and cut as much net free as possible.

One major challenge the team faced was from steel cables tangled within the nets, but

PHOTO KIAN FARIN

PHOTO TIANYI LU

they made steady progress in preparing the site. Meanwhile, Norbert and the science team continued documenting the wreck, photographing both the untouched and damaged parts.

Wrapping up

On the final day of operations, the team focused on trying to cut the net that had been prepared the day before and leaving some extra time to wrap up tasks to leave the site in a safe, prepared state. They cleared the wreck of tools and equipment and prepared any remaining nets for later removal. The steel cinch cables proved problematic in making progress with the nets that remained, and no net was recovered that final day. Despite this, by the end of the day, the wreck was fully cleared, environmental documentation was completed, and all salvageable nets were handed over to a local partner for recycling.

Achievements

Over five days and 15 dives, the UB-88 cleanup project removed around 900 kg/2,000 Ib of

ghost nets. The operation cleared the wreck, but it also kicked off a long-term scientific study to better understand the effects of nets on underwater habitats. A large portion of the recovered debris was sent to a facility for recycling, supporting efforts to create sustainable solutions to marine pollution.

This project highlighted the power of collaboration among various stakeholders, including divers, surface crew, media, and sponsors. Looking ahead, the team plans to return with specialized tools to tackle the steel cables and finish removing the remaining nets. The first phase of the UB-88 cleanup project has made significant progress in marine conservation, showing the positive impact of teamwork in preserving both historical artifacts and marine ecosystems. While there is still much work to be done, this effort serves as a valuable example for future conservation initiatives.

Curtis and his JJ getting back on the boat after a successful dive on day one. PHOTO JAMIE MITCHELL

TEAM MEMBERS

Angie Biggs, Curtis Wolfslau, Daniel Pio, David Watson, Jamie Mitchell, Jim Babor, Juan Torres, Jung-han Hsieh, Karim Hamza, Katie McWilliams, Kian Farin, Laurie Dickson, Mark Self, Michael Gasbarro, Nir Maimon, Norbert Lee, Rene Tetter, Shane McWilliams, Symeon Delikaris Manias, Tianyi Lu, Yury Velikanau & Katie Papac

Gözde Akbayir is the Media & Marketing Manager for Ghost Diving USA and the Marketing Coordinator for GUE. With over 15 years of experience managing a dive center, travel agency, and marketing initiatives, she brings her extensive expertise and love for the ocean to her work. Certified as a trimix instructor, and CCR and cave diver, Gözde specializes in digital marketing, community management, and content creation within recreational and

technical diving. She holds degrees in management and finance, which complement her professional focus. Originally from Türkiye and now residing in Malta with her family, Gözde draws constant inspiration from the sea. Through her roles with Ghost Diving USA and GUE, she is dedicated to supporting marine conservation efforts and amplifying awareness of environmental initiatives.

Jim Babor is a classical musician and has been a member of the Los Angeles Philharmonic since 1993. Jim is also a professor at the University of Southern California Thornton School of Music. He is also an accomplished technical and cave diver and holds certifications from GUE for cave, technical, and rebreather diving.

As for Ghost Diving, Jim has been very generous in donating his time since 2012. He is the current CEO of Ghost Diving USA and has helped propel the organization into one of the most active chapters in the world, as well as aided in the establishment of Ghost Diving USA, an official 501(c)(3) nonprofit corporation, to further the cleanup of coastline around the USA.

Jim Babor

Gözde Akbayir

– The role of divers in conservation

NATIVE SAVING EUROPE'S

The white-clawed crayfish is an emblem of Europe’s freshwater ecosystems, but its survival is under threat. Invasive North American crayfish species, carriers of the crayfish plague, have ravaged native populations since their introduction in the 1970s. Despite being listed as endangered by the IUCN and protected by European law, the future of this species hangs in the balance. In response, conservationists have established ark sites—refuges where native crayfish can thrive away

NATIVE CRAYFISH

from invasive counterparts. These efforts rely on habitat monitoring, with divers playing a crucial role. Through citizen science initiatives, divers are helping to track crayfish populations and support these ecosystems. This article dives into the Midland Pools Project, where divers have explored quarries turned conservation sites. From the heritage of Newbold Quarry to the resilience of Ensor’s Pool, their work offers hope and insights into saving these native crustaceans.

TEXT ROBERT CORBY & MARTIN MAPLE

PHOTOS MIKE CROSS, MIKE WADDINGTON, MARTIN MAPLE & ROBERT CORBY

White-clawed crayfish can be conserved by relocating them to isolated “ark sites,” with citizen science reducing costly monitoring efforts.

“White-clawed crayfish are listed as endangered on the IUCN Red List of Threatened Species and are protected by European law.

PHOTO MIKE CROSS

The UK has one species of native freshwater crayfish, the whiteclawed crayfish Austropotamobius pallipes. Since the 1970s, they have declined in English rivers, having fallen victim to competition from non-native species, most notably the North American signal crayfish (Pacifastacus leniusculus), and a disease called crayfish plague that they carry.

Crayfish plague is caused by the water mold Aphanomyces astaci, which has a swimming spore that can transmit from infected or recently dead animals. The fungus attaches to thin areas of the cuticle and grows through the tissue. It is fatal to European crayfish within two weeks of infection. In the absence of crayfish, A. astaci is cleared from the water within about two weeks.

White-clawed crayfish are listed as endangered on the IUCN Red List of Threatened Species and are protected by European law. All the crayfish monitoring described in this article met the requirements of the regulations and used approved method statements and risk assessments under appropriate levels of professional supervision.

In order to conserve white-clawed crayfish, new populations can be established by relocating individuals into suitable “ark sites.” These are river head pools or, ideally, lakes that are isolated from invasive species. Ongoing monitoring helps to confirm the continued health of the populations but is very expensive. Citizen science projects can offer a cost-effective solution to this.

Midland Pools project

The counties of Leicestershire and Warwickshire in the English midlands are as far from the sea as you can be in Great Britain. However, there is an industrial legacy that has left water-filled quarries across the region.

Since 2018, we have been working with local landowners and site managers at six sites (see table on page 30). In the past, these quarries extracted various minerals, including clay for brickmaking and granite or slate for building, but each quarry has now been returned to nature and forms part of the industrial heritage of the area. Some also have geological importance.

We established a project with the aim of providing opportunities for scientific diving to the local diving community and to develop divers with the necessary skills to go on to contribute to other citizen science projects. The project was registered with Project Baseline in March 2020.

The project sought to answer the following questions:

1. What is in the quarry pools?

2. Is the aquatic environment favorable or unfavorable?

3. Is the aquatic environment improving, declining, or remaining the same?

The project objectives are to:

• Identify divers who are interested in participating in diving projects and provide them with opportunities to safely build capacity

• Carry out historical research on the sites and compare this with submerged evidence

• Map the quarry pools by various methods

• Set up a visibility and temperature monitoring station at each site

• Survey the wildlife present

• Sample the water for chemical analysis

• Remove litter

A team was recruited from the local diving community, and over multiple project days we dived the quarry pools and recorded what was there (wildlife and cultural heritage), collected water samples for chemical analysis, installed monitoring stations (including temperature loggers), and made visibility measurements. We also recovered huge amounts of surface and submerged litter from the water.

In this article we focus on the monitoring of freshwater crayfish in selected ark sites.

Newbold Quarry

Newbold Quarry is a former blue lias (limestone and shale) quarry in the village of Newbold-onAvon in Warwickshire. Lime was made at the

Newbold Quarry, a former limestone quarry in Warwickshire, became a Local Nature Reserve in 1991 and is home to white-clawed crayfish.

site from 1850, but flooding stopped operations in 1923, and it closed in 1927. The quarry was used as a canal reservoir until the 1980s and was taken over by the local authority in 1991 to form a Local Nature Reserve. White-clawed crayfish had been recorded at this site.

A GPS-located base station was set up on one of the 6 m/20 ft shelves comprising a Secchi disk and temperature logger. Subsequently, we have added temperature loggers near the surface and at 15 m/50 ft to investigate inter-seasonal changes in surface and bottom temperature. The quarry contains the buried remains of a blockhouse and small pumping barge, along with rail tracks that would have carried tubs for conveying limestone out of the quarry. As with all the sites in this project, cars have been dumped in the water, mostly from before the 1990s.

The team confirmed the presence of whiteclawed crayfish during wildlife surveys between May 2018 and August 2020. The sedimentary rock walls provide refuges for crayfish, and water

chemistry showed (amongst other results) favorable levels of calcium and magnesium, required for crayfish exoskeleton development and moulting, and low levels of phosphate and nitrate, which at high levels cause eutrophication.

Diver surveys

Numerous fish species were recorded, including pike, perch, bullhead, carp, and roach, as well as freshwater sponges. Zebra mussels ( Dreissena polymorpha ), which are a non-native species, were also found colonizing hard surfaces.

Unfortunately, signal crayfish were observed by the team in November 2021, possibly having entered the pool from the adjacent Oxford Canal, which is only 50 m/165 ft away, or from introduction by people. These included both males and berried (egg-carrying) females, and so a breeding population could be establishing itself. It is likely that these crayfish were also infected by crayfish plague. No further sightings of white-clawed crayfish have been made.

PHOTO MIKE WADDINGTON

Stoney Cove is a popular inland diving site that also supports a population of crayfish.

While diver surveys are considered the most effective method of monitoring crayfish in water over 40 cm/15 in deep, since traps are size-selective and avoided by berried females, an emerging monitoring technique is environmental DNA (eDNA) analysis. To confirm the presence of crayfish species and plague, we are collaborating with other groups to obtain eDNA analysis of water samples. This could help establish the source of the invasive species.

Factors such as population density and competition can drive emigration of signal crayfish. Invasive species are more frequent dispersers due to their higher levels of activity and boldness, and they have been recorded moving up to 1 km/0.6 mi in a single day.

There is also the possibility that signal crayfish were introduced by people. Reasons for this include foragers stocking the pool to harvest the increased numbers at a later date or, more sinisterly, as a retaliation for the increased enforcement of the prohibition of fishing at this site, which led to recent local opposition.

Ensor’s Pool

Ensor's Pool in Nuneaton, Warwickshire, is a former clay pit, and the extracted Etruria marl was used for brickmaking. It is a Site of Special Scientific Interest (the highest level of importance in Europe) for the population of whiteclawed crayfish, estimated to contain a remarkable 50,000 animals.

Sadly, it has been assumed that the population went extinct following the release of a signal crayfish into the pool that had been rescued by an animal welfare charity. A government-sponsored trapping survey in September 2014 found no crayfish present.

This site was found to contain submerged industrial heritage, including the remains of trackways, tubs, and a series of telegraph poles. A Secchi disk and temperature logger were set up on one such pole at a depth of 8 m/26 ft.

During our wildlife surveys, the team was able to confirm the presence of white-clawed crayfish on three occasions:

PHOTO MARTIN MAPLE

Citizen science is key to conserving white-clawed crayfish, with divers mapping habitats, monitoring populations, and supporting the creation of protected "ark sites."

• Two white-clawed crayfish observed, 7 June 2020;

• Eight white-clawed crayfish observed, 26 October 2020; and

• Two white-clawed crayfish observed, 27 February 2021.

It should be noted these were daytime sightings of animals out in the open and not the result of a systematic nocturnal search. The low numbers are therefore not of particular concern; their presence is the key finding. No invasive crayfish species were found.

The reasons for the survival of white-clawed crayfish at this site are not clear. Given only a single invasive crayfish was apparently introduced, it must be assumed that this was not a berried-female, and so a population of signal crayfish was not able to establish. The rapid white-clawed crayfish population crash was most likely the result of crayfish plague, and although pollution cannot be ruled out, there is no evidence for this. While it is assumed that plague would wipe out the entire population, in

this case, a small number of crayfish did survive. This could either be due to resistance to plague, which would be extremely exciting albeit not totally unprecedented, or possibly that the population density became too low for effective disease transmission.

The water chemistry was found to be broadly favorable to crayfish, with no evidence of eutrophication. Fish species are less diverse compared with Newbold Quarry, with perch being the main species. Zebra mussels are also observed at this location.

Check, clean, dry

The questions of whether the environment is favorable or not, and whether it is improving or declining, are more complicated to answer than expected at the start of the project and depend upon the baseline parameters and assumptions from which the assessment is made. Of course, the problem of changing baselines was identified many years ago and is one reason for Project Baseline being established.

The presence of non-native species is of concern, albeit (for example) the zebra mussels observed are extremely common and do not appear to be causing harm. The presence of a signal crayfish is more concerning, and a breeding population in Newbold Quarry does pose an immediate threat to the survival of the native crayfish population at that location.

Litter is also a threat to wildlife. While anglers can inadvertently spread water borne diseases, the more immediate threat to wildlife comes from the snagging and loss of hooks and line. We have observed that at both the sites described here, birds have died due to ingestion of angling hooks. While public awareness of socalled “ghost fishing” gear in the sea is increasing, its presence in freshwater lakes goes largely unobserved.

People provide a means for invasive species to hitch a ride from one location to another, most often accidently but sometimes intentionally. Divers are less likely to transfer material from site to site compared to anglers, but it is still important that we:

1. Check equipment, boats, and clothing after leaving the water for mud, aquatic animals, or plant material and remove anything you find, leaving it at the site.

2. Clean everything thoroughly with fresh water.

3. Dry everything for as long as possible before using it elsewhere.

For our part, the monitoring project continues. We have established links with other local authorities and this summer carried out systematic crayfish surveys under license to support partners in establishing new ark sites from these populations.

ACKNOWLEDGEMENTS

We are grateful to the British Sub-Aqua Jubilee Trust for providing funding, and to the site owners and operators for permission to dive, and our volunteer divers for giving up their time.

PHOTOS

MIKE WADDINGTON, MARTIN MAPLE & ROBERT CORBY

SUMMARY OF SITE CHARACTERISTICS

PRIOR TO THIS PROJECT

Martin graduated from the University of St Andrews with a degree and PhD in chemistry in 2003. He has worked in energy consultancy for the past 18 years, with a recent focus on hydrogen as a green fuel. He learned to dive with BSAC in 2013 and is currently a BSAC Advanced Diver and Open Water Instructor, and serves as Diving Officer of his local BSAC branch. He joined GUE in 2018 and has completed

Tech 1, Cave 1, and CCR 1 classes, as well as a recreational ITC. He has a particular interest in cold water wreck diving and scientific diving. He is coproject manager of Project Baseline Midland Pools, which was awarded the Prince of Wales Prize in 2022. Martin is a trustee of Project Baseline UK and has volunteered with Ghost Fishing UK, various Project Baseline initiatives, and the HMS Exmouth project.

Rob began diving in 2015 with a BSAC Ocean Diver qualification for holiday diving, but he soon fell in love with UK diving. He progressed to BSAC Advanced Diver and is Chairman of Marlin Sub-Aqua Club, co-managing Project Baseline Midland Pools. Involved with GUE since 2019, Rob holds a Tech 1 certification and plans to become CCR certified this year.

Drawn to GUE for its standardization and project diving skills, he has contributed to projects in Scotland and is an active member of Ghost Fishing UK. A Trainee Advanced Clinical Practitioner, Rob is completing an MSc this year while balancing his career with family life, including his wife and two young sons.

Robert Corby

Martin J Maple

CCR FUNDAMENTALS

PHOTO JESPER KJØLLER

FUNDAMENTALS

– Redefining entry-level rebreather training

GUE’s

Closed-Circuit Rebreather (CCR) Fundamentals course marks a transformative step in rebreather training and offers an accessible and streamlined path for divers transitioning from open-circuit systems. This brandnew program focuses on refining foundational skills while addressing the unique challenges of rebreather diving.

Designed as a bridge to deep technical diving, CCR Fundamentals embodies GUE’s commitment to precision, safety, and practical excellence and provides a tailored entry point for divers ready to explore the next frontier.

“As GUE’s understanding of rebreather training progressed over the years, the entire diving community evolved as well.

Graham Blackmore at Deep Dive Dubai, introducing the new CCR Fundamentals to the first group of GUE instructors during the inaugural Instructor Training Course.

PHOTO JESPER KJØLLER

The journey to the current CCR training program began in 2013 when GUE launched its first CCR classes. At that time, the course had a Technical Diver Level 2 entry requirement. Leadership had always envisioned that these initial classes would eventually evolve; GUE planned a follow-up Level 2 CCR class to offer a deeper dive into the complexities of rebreather diving. However, it took until 2019 to finalize the curriculum and produce the first batch of Level 2 instructors, with classes following shortly thereafter (see Quest Vol. 22, No. 3 – August 2021). At that point, the first clas's name changed to CCR 1, and the entry requirements were relaxed; divers only needed to complete Technical Diver Level 1 and 25 open-circuit technical dives. Richard Lundgren, GUE’s director of technical and CCR training at the time, and Jarrod Jablonski played pivotal roles in shaping the initial program's development. They taught the first beta CCR classes, which included many experienced technical and cave instructors such as Bob Sherwood, Mario Arena, Guy Shockey, Mark Messersmith, and even the author. Richard Lundgren, in particular, was a driving force behind bringing together a vast body of knowledge about rebreather diving and packaging it into a coherent training system. He introduced new concepts such as a pre-dive sequence and checklists that are attached to tanks; these were designed to enhance diver safety and preparation. Additionally, Dave Thompson from JJ-CCR participated in auditing early classes to ensure that the curriculum was both practical and safe.

Changing paradigms

As GUE’s understanding of rebreather training progressed over the years, the entire diving community evolved as well. At first, GUE (along with many other dive organizations) expressed

skepticism about electronic rebreathers; early adopters were often jokingly asked whether they were bringing their Tamagotchi when organizing dives with friends. This skepticism was largely based on the belief that a solid open-circuit background was essential for diving a rebreather. This belief was reflected in GUE’s emphasis on the Technical Diver Level 2 entry point, which required significant open-circuit experience before transitioning to a rebreather. However, things have changed. Helium, once more readily available and at a lower cost than today’s prices, is now subject to much stricter controls and higher costs. Moreover, GUE’s deeper understanding of how to train divers has revealed that open-circuit experience does not always equate to better rebreather divers, and in some cases, the opposite may be true.

New entry point

Around two years ago, after frequent discussions with Derk Remmers and Kirill Egorov, I began to raise the idea with Jarrod Jablonski of changing the entry point for rebreather instruction to create a more efficient training path for divers wishing to pursue deep technical diving. Drawing from the combined experience of over 100 CCR classes taught by Derk and I, as well as feedback from other active instructors, it became apparent that open-circuit experience didn’t necessarily make divers better at rebreather diving. In fact, less experienced divers, when taught properly, could excel in the CCR ecosphere. When considering the logistics of helium availability and the ongoing challenges of its costs, it no longer seemed practical to force divers to gain extensive open-circuit experience before starting their CCR training, especially if their ultimate goal was deep diving. This led to the creation of the CCR Fundamentals class.

Initially, this class was called something else; but, after much deliberation, leadership landed

“Closed-Circuit Rebreather Fundamentals, however, is designed for those who want to dive with a rebreather. It offers a more direct route into technical diving on a rebreather without the need for extensive open-circuit experience.

on Closed-Circuit Rebreather Fundamentals. This was a significant shift in direction for GUE and, naturally, it sparked debates within the organization—particularly among those already deeply invested in the GUE training system. The new entry point for this course is a modest pass at the GUE Technical Fundamentals level, which marks a major departure from traditional GUE training protocols.

Natural next step

It is essential to emphasize that the CCR Fundamentals class is not intended to replace Technical Diver Level 1. The Tech 1 class remains a core part of the GUE training system and will continue to offer an excellent path for many divers progressing to deeper diving. For divers not yet diving regularly in technical conditions (generally, around 10 or more dives per year), open-circuit diving remains a simpler, more cost-effective, and arguably safer option. Technical Diver Level 1 remains the best path for many divers after completing GUE Technical Fundamentals.

Closed-Circuit Rebreather Fundamentals, however, is designed for those who want to dive with a rebreather. It offers a more direct route into technical diving on a rebreather without the need for extensive open-circuit experience. For divers aiming to reach depths where decompression times increase and the rebreather becomes the best tool for the job, this course is the natural next step. Diving to depths of 60 m/200 ft or greater and facing decompression times of one hour or more clearly benefits from the use of a rebreather, which offers enhanced safety compared to open-circuit diving.

Simplification

Divers familiar with the previous CCR Level 1 course will recognize CCR Fundamentals as a simplified version of that gateway program. As the new entry point for GUE CCR training, the focus is now on the essential skills needed for CCR diving, and the class follows a standardized configuration with no BOV (bailout valve). Gas plans and reserves have been simplified

PHOTO DERK REMMERS

With proper training, less experienced divers can excel in the CCR ecosphere. With helium availability and cost challenges, requiring extensive open-circuit experience before CCR is impractical, leading to the CCR Fundamentals class.

to increase safety, and divers will primarily use nitrox mixtures while staying within minimum decompression limits. The maximum depth for the course and the subsequent certification limit is 30 m/100 ft, allowing plenty of room for divers to gain more experience and prepare for deeper, more complex training. A new configuration, referred to as the “small rig,” includes manifolded 3 L/23 ft3 diluent tanks and a smaller oxygen bottle. This is a departure from the larger configurations used for more advanced dives.

One key element that is not included in the CCR Fundamentals Diver course is failure resolution. There are no scenario-based exercises where divers must identify faults and bail out. The focus is on core skills, and failure resolution will be introduced in more advanced courses. The CCR Fundamentals Diver course is considered a stepping stone and, as such, it aligns with ISO standards to ensure that divers are ready to move on to the more technical aspects of rebreather diving.

A new pathway

However, introducing the CCR Fundamentals course also presents several challenges. One of the primary concerns is how divers will transition into technical diving after completing the course. Divers who have already completed Technical Diver Level 1 will also wonder if they will now have to take an additional CCR class to reach the same point in their education as they would have before. To address these concerns, GUE has created a pathway for divers to progress from CCR Fundamentals to CCR Technical Diver Level 1 after gaining 50 hours of dive experience.

The new CCR Technical Diver Level 1 class will build on the skills learned in the CCR Fundamentals Diver class, with a focus on deep diving and decompression techniques, allowing divers to dive to depths up to 51 m/170 ft and undertake decompression dives lasting up to 30 minutes. The course will introduce skills such as teamwork, open- and closed-circuit failure handling, and decompression management.

PHOTO KIRILL EGOROV

To start the CCR Fundamentals course, you need to have a Technical Fundamentals certification (or Fundamentals with Technical pass) and at least 150 dives.

“The introduction of the CCR Fundamentals class and its accompanying changes to the training system represents a major shift in how GUE approaches rebreather training.

In October 2024, a group of GUE Instructor Candidates, Instructor Trainers, and Instructor Evaluators came together to beta test the courses and provide valuable feedback.

This class mirrors much of the content of the Technical Diver Level 1 course but with an emphasis on rebreather diving. While the CCR Fundamentals class is a crucial step in a diver’s journey, it should be viewed as just that—a step towards technical diving rather than an endpoint. Rebreathers are not necessary for recreational dives but are invaluable tools for deeper, longer dives where the cost and complexity are offset by the benefits they bring.

Divers with a Technical Diver Level 1 certification will already possess many of the necessary skills for technical CCR diving. However, they must still learn how to operate a rebreather. Thus, completing the CCR Fundamentals class is a prerequisite for those divers wishing to transition to rebreather diving. After gaining experience, these divers can take an upgrade class to ensure that their diving capacity is appropriate for advanced technical diving. This class will focus on rebreather failure management, ascents, bailouts with decompression obligations, and conducting decompression procedures.

Streamlined CCR progression

These changes to the GUE course progression offer a key improvement: the introduction of CCR Technical Diver Level 1 and upgrade classes. Previously, divers completing CCR Level 1 were certified to dive to depths of 51 m/170 ft with up to 30 minutes of decompression without ever verifying whether they had the necessary skills for more complex technical diving. The revamped program ensures that instructors continually assess and improve divers’ skills as they progress to higher-level courses.

Another key development is the clarification of CCR and open-circuit capabilities. CCR Tech 1 divers are trained to dive to 51 m/170 ft with 30 minutes of decompression and are capable of bailing out to open-circuit if necessary. However, they are not qualified to dive with open circuit for these depths unless they complete a component of the class that qualifies them for open-circuit dives. Both closed circuit technical classes (CCR-T1 and CCR-T2) will have a component that allows open-circuit qualification for

interested divers. This offers more clarity for divers who may wish to pursue both types of diving.

A major switch

The introduction of the CCR Fundamentals class and its accompanying changes to the training system represents a major shift in how GUE approaches rebreather training. The goal is to provide divers with the best path to becoming competent technical CCR divers without unnecessary complexity. The chang-

Graham Blackmore, GUE’s technical and CCR program director, is a lifelong diver with a deep-seated passion for the ocean. Born and raised near the sea in the UK, he pursued his fascination with marine life by earning a PhD in marine biology.

Kirill Egorov, John Kendall, Graham Blackmore, and Derk Remmers (L to R) engaged in a lively surface discussion following an ITC dive.

es are designed to be safer, more efficient, and more adaptable to the evolving needs of divers.

With the support and input of colleagues like Jarrod Jablonski, Kirill Egorov, Mario Arena, Kees Beemster Leverenz, Derk Remmers, Guy Shockey, and John Kendall, the new structure promises to enhance GUE’s training system, offering divers clearer pathways and better opportunities to achieve their technical diving goals.

However, his true calling lies in the underwater world, leading him to a career as a global diving instructor and explorer. While he enjoys all aspects of diving, his British heritage lends him a particular fondness for wreck diving.

PHOTO DERK REMMERS

Graham Blackmore

FACT FILE // CCR FUNDAMENTALS FAQ

Do I need to complete CCR-F and then CCR-T1 if I already have a Tech 1 certification?

If you already have a Tech 1 certification, you will still need to complete CCR-F (Closed-Circuit Rebreather Fundamentals Diver), but you won’t need the full CCR-T1 (Closed-Circuit Rebreather Technical Diver Level 1) course. The CCR-F course is designed to teach the basic operation of the rebreather, and this foundational knowledge is essential for rebreather diving. Since you already possess significant technical diving skills, these will help you during the CCR-F course, and after gaining adequate experience and capacity on the rebreather, you will be eligible to complete an upgrade from CCR-F to CCR-T1. This upgrade will allow you to proceed to deeper dives and more advanced technical skills specific to CCR diving.

Is it true that CCR-F may be done in a smaller setup?

Yes; for the CCR-F course, you can use a smaller setup. For example, a configuration with D3/23 ft3 bailout and smaller oxygen bottles (1.8 L in Europe or 2 L in North America) would be ideal for diving to a maximum depth of 30 m/100 ft while you build your experience and capacity. This allows you to start with a manageable system before progressing to larger and more complex setups.

Why are there no helium-based diluents in CCR-F?

The CCR-F course is designed as a basic user class with a maximum depth of 30 m/100 ft and does not involve the use of helium-based diluents. This keeps the focus on familiarizing divers with the basic operations of the rebreather before diving deeper and with helium-based gases.

Can I carry a decompression tank after CCR-F?

No, the CCR-F class does not involve the use of decompression tanks or stages. Even if you are certified to carry a decompression or stage cylinder through other certifications, CCR-F focuses on building familiarity with the rebreather itself. Carrying additional tanks would distract from this goal. It’s advisable to focus on gaining experience with the rebreather before adding more complex equipment.

Why would I use a CCR in the 30 m/100 ft range?

The use of a CCR in the 30 m/100 ft range may seem unnecessary to some, but the CCR-F course focuses on familiarizing divers with the rebreather at this depth. In this range, it’s not about necessity but about building experience, comfort, and capacity with the rebreather before progressing to deeper depths where its advantages become more evident.

Is CCR-F a result of increasing helium prices?

While the price of helium has become more of a concern for active deep divers, the main motivation for the introduction of CCR-F was to improve training quality for divers progressing into rebreather diving. For most divers, the rebreather’s cost and maintenance will far exceed the cost of helium for some years, but the program aims to streamline training and provide a solid foundation in rebreather diving regardless of helium prices.

I still prefer open-circuit diving. Do I have to use a CCR now to be part of GUE activities?

No, you do not have to switch to a CCR to participate in GUE activities. GUE continues

to value and promote open-circuit diving for those who prefer it. For many divers, opencircuit remains the safest, most cost-effective, and easiest way to conduct technical dives. The introduction of CCR-F simply allows divers to gain the necessary rebreather skills for deeper diving.

How do I progress to CCR Cave?

To take GUE’s CCR Cave course, you must be certified as a Cave 2, CCR-F, and CCR-T1 diver. GUE’s training emphasizes the importance of mastering failure management in open-water environments before introducing it in overhead environments like caves. Therefore, the training path ensures that you have a strong foundation before progressing into more complex environments.

Can I proceed to CCR-T1 directly if I have a lot of CCR experience from another agency?

If you have substantial CCR experience from another agency, completing CCR-F will still likely benefit you and align you with GUE procedures and standards. GUE Standards allow for waivers in certain circumstances, but each request is assessed on a case-by-case basis. If you feel your experience is sufficient, it’s best to discuss the waiver process with your instructor.

Do I need to buy a JJ-CCR to do the course?

No, you do not need to purchase a JJ-CCR specifically for the course, but you will need to have access to one during both the course and your subsequent experience dives.

How many dives do I need before proceeding to CCR-T1?

After completing CCR-F, you need to complete a minimum of 50 CCR dives in the GUE configuration before you can progress to

CCR-T1. It’s important to feel comfortable with basic operations: performing a mid-water ascent, managing decompression ascents in complete control, and following lines to 6m/20 ft.

How many dives do I need to start a CCR Fundamentals course?

To start the CCR Fundamentals course, you need to have a Technical Fundamentals certification (or Fundamentals with Technical pass) and at least 150 dives.

Is the rebreather unit still a JJ-CCR in a GUE configuration?

Yes, GUE’s approved CCR is the modified JJCCR setup. This ensures uniformity and safety during training.

Can I take CCR-F with the JJ-CCR in factory configuration?

No, the factory configuration of the JJ-CCR is not acceptable. The course requires the GUEconfigured unit to ensure standardization as divers practice GUE skills and procedures.

My JJ-CCR is already configured with double 7 L or double 40 ft3 cylinders; do I need to change it for CCR-F?

Both double 7 L or double 40 ft3 cylinders are acceptable for the CCR Fundamentals course. However, any changes would depend on discussions with your instructor, so it's important to verify with them.

How will my experience dives be verified before pursuing the next level of training?

Your CCR logbook will need to be submitted to your instructor for verification. It’s best to download your logbook from your rebreather’s Shearwater handset for a detailed record of your dives.

Passionate storyteller STEFAN PANIS

Stefan, a Belgian photographer, began diving at a young age and soon transitioned to film photography. Later, he became a technical CCR diver and acquired his first digital camera in 2012. As an avid diver, Stefan has participated in numerous dive projects worldwide. He documented his dives in the Belgian mines and the shipwrecks in the Dover Straits, which became his preferred dive sites.

TITLE The Winch LOCATION Belgium

CAMERA Nikon D850

HOUSING Easydive

LENS Sigma 15mm Fisheye

EXPOSURE f/5.6, 1/30, ISO 400

LIGHT Dual Subtronic pro + slave

Subtronic

Stefan’s work gained recognition, and he went on to write for several international magazines and publish five books. He continues to expand his horizons and enjoys traveling to capture his underwater adventures. He also participates in various dive shows where he enthusiastically shares his experiences. In recent years, Stefan has launched his own dive show in Belgium, called Dive-Expo, where he and other passionate divers showcase their experiences.

www.stefpanisphotography.com

TITLE The Blue

LOCATION Belgium

CAMERA Nikon D850 HOUSING Easydive

LENS Sigma 15mm Fisheye

EXPOSURE f/5, 1/30sec, ISO 500

LIGHT Dual Subtronic pro + slave Subtronic

Lagoon

TITLE White Paradise

LOCATION Belgium

CAMERA Nikon D850

HOUSING Easydive

LENS SIGMA 15mm Fisheye

EXPOSURE f/6.3, 1/30sec, ISO 500

LIGHT Dual Subtronic pro + Inon 240 slave strobe

TITLE The Shaft

LOCATION Martelange slate mine

CAMERA Nikon D850

HOUSING Easydive

LENS Sigma 15mm Fisheye

EXPOSURE f6.3, 1/30sec, ISO400

LIGHT Dual Subtronic pro + slave Subtronic

TITLE Black Marble Beauty

LOCATION Belgium

CAMERA Nikon D850

HOUSING Easydive

LENS Sigma 15mm Fisheye

EXPOSURE f/6.3, 1/30, ISO 400

LIGHT Dual Subtronic pro + slave Subtronic + slave Inon 240

TITLE Sweet Little Slate Mine

LOCATION Belgium

CAMERA Nikon D850

HOUSING Easydive

LENS SIGMA 15mm Fisheye

EXPOSURE f/6.3, 1/30sec, ISO 400

LIGHT Dual Subtronic pro + slave Subtronic

TITLE Cenote Warnant

LOCATION Warnant, Belgium

CAMERA Nikon D850 HOUSING Easydive

LENS Sigma 15mm Fisheye

EXPOSURE f/5.6, 1/30sec, ISO 400

LIGHT Dual Subtronic pro

TITLE Dreamgate

LOCATION Yucatan, Mexico

CAMERA Nikon D850 HOUSING Easydive

LENS Sigma 15mm Fisheye

EXPOSURE f/7.1, 1/30sec, ISO 500

LIGHT Dual Subtronic pro + slave strobe Subtronic

SYMBIOS

PHOTO JULIAN MÜHLENHAUS

– A revolution in rebreather diving

TEXT JOHN KENDALL

PHOTOS JULIAN MÜHLENHAUS & JESPER KJØLLER

GUE Instructor John Kendall ready for yet another test dive of the Halcyon Symbios in

Deep Dive Dubai.

PHOTO JESPER KJØLLER

Halcyon Manufacturing is set to redefine rebreather diving with the launch of the Symbios, a compact, chestmount closed-circuit rebreather (CCR) designed for maximum flexibility and performance. Debuting at the 2024 DEMA show, the Symbios combines cuttingedge wireless technology, a lightweight design, and unmatched versatility for both recreational and technical divers.

GUE diving instructor and Halcyon R&D team member

John Kendall provides insights into the Symbios’ development and groundbreaking features, showcasing how this innovative unit is poised to transform underwater exploration for divers worldwide.

Ever since Halcyon Manufacturing entered the scene, the company has enabled divers with novel tools to enrich their diving adventures. Halcyon’s unique PVR-BASC (passive, variable-ratio, biased addition), also known as “The Fridge,” was a semi-closed rebreather first built in 1994 and a vital element of the company’s early history. This distinctive semiclosed-circuit rebreather has allowed countless adventurous divers to travel thousands of kilometers into the longest and deepest caves on the planet.

Subsequent iterations—the RB80 and RB-K— refined the pioneering concepts of these early units. Halcyon rebreathers, known for their robust construction and reliable operation, have been and continue to be at the forefront of exploration projects as both primary and bailout/ redundant units for divers worldwide.

Historically, Halcyon divers and principals have used both semi-closed and fully closed rebreathers, adapting to the demands of spe-

cific dives. These projects revealed the value of a flexible rebreather configuration. Halcyon began using the RB80 as both a backmount and a staged sidemount rebreather in the early 2000s, a practice that evolved into its use in small caves for sidemount diving. The pursuit of a smaller, more flexible rebreather culminated in the latest addition to the Halcyon family: the Halcyon Symbios Rebreather. Compact, versatile, and high-tech, this rebreather meets the needs of “tecreational” and hardcore technical divers, conforms to a wide range of equipment configurations, and satisfies diverse dive requirements.

Why chestmount?

There are many reasons for using a chestmount rebreather instead of, or alongside, a traditional backmount unit. Initially, the team was drawn to the flexibility of adding the Symbios to sidemount or backmount setups. Over time, the ease of use and tremendous adaptability revealed a broader potential: the Symbios can easily integrate into almost any configuration.

“Compact, versatile, and hightech, this rebreather meets the needs of “tecreational” and hardcore technical divers, conforms to a wide range of equipment configurations, and satisfies diverse dive requirements.

The chestmount design is ideal for new rebreather divers, allowing them to keep their existing cylinder setup and easily clip the rebreather onto their chest for a smoother learning curve.

PHOTO JULIAN MÜHLENHAUS

Seen from above, a group of Symbios divers appears similar to regular open circuit divers. The only giveaway is the absence of exhaust bubbles.

Industry-leading technology and an exceptionally small form factor (7.5 kg, 37 x 30 x 12 cm/16.5 lb, 15 x 12 x 5 inches without a tank) significantly enhance this flexibility. The compact size makes the Symbios attractive to traveling divers seeking a lightweight package with the capacity of much larger rebreathers. Whether traveling to remote dive sites or navigating dry caves to reach a sump, the Symbios has proven remarkably capable.

A chestmount configuration is also advantageous for divers new to rebreathers, as they can retain their existing cylinder setup and simply clip the rebreather onto their chest. This design provides a friendlier learning curve for novice rebreather divers.

Development of the Symbios

Chestmount rebreathers were among the first rebreathers ever built, so what makes the Halcyon Symbios unique? Three significant features set it apart.

The first is its completely wireless platform. The Symbios CCR uses redundant wireless

transmitters to relay all forms of data—including the pO2 of all three sensors and O2 pressure via an onboard pressure transmitter. Divers familiar with the frustrations of cabling will appreciate the wireless system, which eliminates tangled wires and enhances comfort and utility. The Symbios can send data to a handset and/or HUD without cables, and divers can even receive and read data from their dive buddies and students.

The Symbios integrates seamlessly with the Symbios wireless ecosystem, supporting pressure transmitters, navigation systems, GPS receivers, and operational specs for DPVs, lights, and trim sensors. Its wireless system employs magnetic transmission technology, ensuring higher data rates and reliability, with data sent twice per second.

The next innovation is the integrated BOV/ ADV. The bailout valve is positioned on the chest and doubles as an ADV, allowing the diver to easily switch between CCR and open-circuit. The design avoids the drawbacks of traditional mouthpiece-based BOVs, such as weight and jaw fatigue.

PHOTOS JESPER KJØLLER

Oxygen sensing

A proprietary solid-state oxygen sensor developed with Oxygen Scientific is another significant evolution. The Greenflash sensor, powered by a small CR2477 battery, can function as a plug-in replacement for traditional galvanic oxygen sensors or output digital signals. In the Symbios, this system combines analog and digital sensors for enhanced reliability, mitigating risks like water accumulation and ensuring accurate oxygen readings in the breathing loop.

The Symbios chestmount system integrates well with a standard GUE configuration.

Despite its compact size, the Symbios is a remarkably capable electronic CCR. Its lightweight design (7.5 kg/16.5 lb for travel and under 11 kg/24 lb ready to dive) and 2.7 kg/6 lb scrubber offer long dive durations and easy portability, fitting into a small backpack.

The Symbios is currently undergoing CE certification, with the first units expected to launch in non-CE countries by the end of the year. Major training agencies, inclding GUE will offer Symbios training, and pricing is expected to be competitive, considering the remarkable benefits of this groundbreaking technology. 

John Kendall is a GUE technical, cave, and CCR instructor who has turned his lifelong fascination with the underwater world into a global teaching career. He builds local GUE communities and pioneers underwater 3D photogrammetry for nautical archaeology, creating digital models of shipwrecks and caves. John authored the GUE

Photogrammetry class and serves on the GUE Training Council. A Fellow of the Explorers Club, he also joined Halcyon Manufacturing's R&D team, focusing on their new CCR. His work combines exploration, education, and innovation, helping researchers navigate underwater sites with unparalleled ease from their computers.

John Kendall

PHOTOS JESPER KJØLLER

FACT FILE // SYMBIOS SPECS

CONTROLLER

Primary controller

Onboard physical button with wireless monitoring

Redundant controller Optional corded controller/HUD/Buddy Light

Secondary electronics/pO2 Redundant "Sentinel" with independent transmitter array

Tertiary electronics Readable by an infinite number of compatible handsets and/or HUD units

SCRUBBER

Scrubber type Axial

Scrubber volume 2.7kg

Temp. stick (scrubber monitoring) No

Scrubber duration CE: CO2 1.6l/m 5mb bypass TBC

LOOP

Work of breathing (WOB) CE 100m test, trimix, horizontal TBC

Work of breathing (WOB) CE 40m test, air, vertical 1.6 joules/liter

Active loop volume (liter) CE Test

Counterlungs Front-mounted

Detachable counterlungs Yes

Oxygen injection Before scrubber

Loop direction Right to left

Automatic diluent valve (ADV) Yes

Diluent shut-off valve No

Bailout valve (BOV) Yes (Built into the ADV system)

Mouthpiece retaining strap Yes

Flood resistance

HEAD & SENSORS

Exhalation lung has purgeable water trap. All electronics sealed from water ingress.

User upgradeable firmware? Yes

Number of solenoids 1

Means of O2 addition Solenoid + MAV

Solid state O2 sensor Yes, Greenflash

Independent secondary O2 reading Yes

Helium sensors No

CO2 sensors No

Dual computers Yes

Independent electronics

Two monitoring systems in head with independent transmitters

Bailout mode No

Battery type Rechargeable

DISPLAYS & WARNINGS

Head-up display (HUD) Fully featured dive computer HUD

Buddy display Optional wired HUD with buddy light

Other active warning devices Vibrating alert in rebreather head

Near eye computer (HUD) Yes

HANDSET

Number of handsets Infinite number of receivers

Pressure reading (air Integration) Yes

Bluetooth on handset Yes

Wi-Fi on handset No

Digital compass Yes

Multi-language interface Yes

CYLINDERS

Cylinder options Multiple options for onboard O2

Onboard multi diluent tank option N/A

Offboard gas feed Yes

FORM FACTOR

Travel/mini version Inherent in design

Stand No

Sidemount conversion Compatible with sidemount bailout configurations

SERVICE & SUPPORT

Supplied ready to dive Yes

Warranty (months) TBD

Worldwide service/support Yes

Recommended service interval Yearly

Cost of service Service center dependent

SHIPPING & ORDERING

Weight ready to dive ~11 KG depending on O2 tank used Manufacturer website www.halcyon.net

CHESTMOUNTEDREBREATHERS

Chestmounted rebreather units represent a fascinating evolution in the field of diving technology, driven by specific needs and innovative engineering. Their compact design, ease of accessibility, and adaptability have made them an appealing alternative to traditional backmounted systems. With GUE’s focus on standardization, safety, and team efficiency, the integration of chestmounted rebreathers presents intriguing possibilities while requiring careful consideration to align with GUE's principles.

CHESTMOUNTEDREBREATHERS

The concept of rebreathers dates back to the early 19th century, when inventors sought ways to recycle exhaled air, making underwater exploration and industrial work more efficient and less dependent on surface air supplies. Early designs, such as those by Henry Fleuss in the 1870s, used closed-circuit systems to scrub carbon dioxide from exhaled air while adding oxygen to maintain breathable levels. These systems were

primarily used for diving, firefighting, and mine rescue operations.

During World War II, rebreathers gained prominence for military applications, particularly among combat divers and submariners. Their stealth capabilities—no bubbles were produced—made them ideal for covert operations.

One of the chestmounted systems was the British "Davis Submerged Escape Apparatus," used primarily for submarine escape. Over time, the design evolved to meet the needs of combat

divers and mine-clearance operations, where maneuverability and low magnetic signatures were paramount. By the late 20th century, civilian applications began to emerge, particularly in technical diving, where explorers sought systems that combined portability with redundancy and operational flexibility.

Chestmounted rebreathers offer several distinct advantages:

1. Compact profile By positioning the rebreather on the chest, divers can reduce their overall in-water silhouette. This is particularly advantageous in environments with tight restrictions, such as narrow cave passages or cluttered wrecks. This feature combined with the ease of temporarily removing the unit make them a favorite among divers pursuing these kinds of dives.

2. Accessibility The front-mounted position ensures that critical components, such as shut-off valves, gas connections, electronics, and manual controls, are easily accessible. In an emergency, this proximity allows divers to more quickly resolve issues compared to back-mounted units.

3. Weight distribution Divers often find that chestmounted units provide better weight distribution, especially when paired with a streamlined back-gas system. This configuration can improve trim and reduce strain on the lower back.

4. Modularity Chestmounted units can be integrated with a variety of setups, including using classic open-circuit systems as bailout systems or secondary rebreathers. This modularity enhances flexibility for complex dives.

5. Reduced work of breathing One of the most significant benefits of chestmounted rebreathers is the reduced work of breathing they offer. In underwater environments, the effort required to inhale and exhale through a rebreather system—known as work of breathing (WOB)—is influenced by the position of the counterlungs, hydrostatic pressures, and the design of the breathing loop.Chestmounted configurations typi-

cally position the counterlungs close to the diver's natural lung position, minimizing the hydrostatic pressure difference between the breathing loop and the diver’s lungs. This alignment allows for a smoother and more natural inhalation and exhalation cycle, reducing physical effort and oxygen consumption during the dive. In contrast, back-mounted rebreathers often position the counterlungs farther from the diver’s lungs, potentially increasing WOB, especially when the diver changes orientation in the water column (e.g., head-down or head-up positions). This increased WOB can lead to fatigue, reduced efficiency, and, in extreme cases, hypercapnia (elevated carbon dioxide levels). Lowering WOB is particularly critical for technical diving, where divers may face extended bottom times, significant depths, and complex tasks. By reducing physical strain, chestmounted rebreathers help divers conserve energy, reduce stress, and maintain clearer cognitive function—all essential factors for managing the risks associated with deep or prolonged dives.

Despite these advantages, chestmounted rebreathers are not without their challenges. They can obstruct access to other equipment, such as drysuit inflators or backup lights, and may alter the diver's center of gravity, requiring adjustments in buoyancy control and trim.

Integration with the GUE Approach

GUE has always emphasized standardization, team-based diving, and rigorous training as the pillars of its approach. The organization has traditionally focused on open-circuit diving and back-mounted rebreathers, so how might a chestmounted rebreather align with its core principles?

1. Streamlined configuration for team awareness The streamlined profile and accessible design of chestmounted rebreathers make them compatible with GUE’s emphasis on maintaining clear communication and situational aware-

Chestmounted configurations position the counterlungs near the diver's lungs, reducing hydrostatic pressure differences and leading to a lower work of breathing (WOB).

PHOTO JESPER KJØLLER

ness within dive teams. By positioning critical components in view, chestmounted systems facilitate quick status checks and team-based problem-solving.

2. Enhanced diver efficiency The reduced WOB offered by chestmounted systems supports GUE’s focus on maintaining diver efficiency and minimizing stress during complex dives. By reducing physiological strain, these systems enhance overall safety and performance, particularly in demanding environments like caves or deep wrecks.

3. Modularity and redundancy GUE’s emphasis on standardization and redundancy is well-served by the flexibility of chestmounted rebreathers. These systems can be seamlessly integrated into GUE-compliant configurations, ensuring compatibility with team diving protocols and providing reliable backup options.

4. Training and preparedness As GUE divers undergo rigorous training to master equipment and protocols, an integration of chestmounted rebreathers would naturally

include an in-depth focus on their unique characteristics and potential challenges. This would ensure that divers are fully prepared to use these systems safely and effectively in real-world scenarios.

Chestmounted rebreather advantages such as reduced work of breathing, improved accessibility, and enhanced modularity make these systems a valuable tool for technical and exploration divers as they navigate challenging underwater environments.

The integration of chestmounted rebreathers with the GUE approach offers exciting possibilities for advancing diving safety and efficiency. By aligning with GUE’s emphasis on streamlined configurations, team-based protocols, and rigorous training, chestmounted systems can enhance the capabilities of divers while staying true to the organization’s core principles. As diving technology continues to evolve, the inclusion of chestmounted rebreathers within GUE’s framework underscores the organization's commitment to innovation and excellence in underwater exploration.

Given unique functions present with the Symbios platform, GUE has been testing this rebreather over the last year and is now moving to include it as an option for GUE rebreather training programs. The current test process is moving into a beta-evaluation phase with expectations for inclusion in 2025.

Born in Athens, Greece, Dimitris Fifis started diving in 1991 and became an instructor in 1998. In 2009, after 23 years of service in the Greek Navy (most of them in the aviation branch), he retired and decided to pursue a full-time career in diving. Since then he has managed diving operations in various diving centers

in Greece as well as on mega-yachts. Dimitris discovered GUE in 2007 and never looked back. He currently lives and works in Dubai, and is involved in various wreck exploration and underwater filming projects in the area along with R&D for the new Halcyon Symbios CCR and the associated training programs.

Dimitris Fifis

CAVE DIVING ACCIDENT

PHOTO KIRILL EGOROV

TEXT FROM THE GUE PUBLICATION DEEP INTO CAVE DIVING WITH CONTRIBUTIONS FROM KIRILL EGOROV,

JARROD JABLONSKI, DANIEL RIORDAN, FRED DEVOS, TODD KINCAID & CHRIS LE MAILLOT PHOTOS KIRILL EGOROV & PETR POLACH

ANALYSIS

Caves

possess a mystical quality that inspires both curiosity and fear. For average people, the prospect of entering a cave, let alone a water-filled cave, probably feels like a less-than-reasonable pursuit.

As a result, over the years, the general public has looked upon cave diving with some degree of misgiving; in fact, many see it as a risk they are unwilling to take. Undeniably, past fatalities have helped stigmatize cave diving. However, an interesting—and, in many ways, positive—aspect is that the risk one faces when cave diving is identifiable, relatively predictable, and, therefore, manageable.

Caves possess a mystical quality that inspires both curiosity and fear. For average people, the prospect of entering a cave, let alone a water-filled cave, probably feels like a less-than-reasonable pursuit. As a result, over the years, the general public has looked upon cave diving with some degree of misgiving; in fact, many see it as a risk they are unwilling to take.

Undeniably, past fatalities have helped stigmatize cave diving. However, an interesting—and, in many ways, positive—aspect is that the risk one faces when cave diving is identifiable, relatively predictable, and, therefore, manageable.

In his 1979 handbook Basic Cave Diving: A Blueprint for Survival, cave explorer Sheck Exley undertook a systematic analysis of the causes of cave diving fatalities. Relying on an examination of previous fatalities, Exley’s analysis sought to outline the primary risks of cave diving. Even today, this form of analysis plays an important role in the evolution of cave diving procedures. In his analysis, Exley observed that

cave diving fatalities could be grouped into three categories (or causes):

• Failure to maintain a continuous guideline

• Failure to reserve two-thirds of available gas for exiting

• Diving deep in caves

Exley’s initial categories managed to delineate the main causes of most cave diving fatalities but failed to account for the relevance of contributing factors. In 1984, inadequate training and insufficient lighting were recognized as significant and contributory causes of cave fatalities and added to Exley’s list. Each of these categories outlined an area of substantially elevated risk and, as a group, is commonly referred to as the five rules of accident analysis. Today, these components remain at the core of all cave training.

Continuous guideline

Failure to maintain a single, continuous guideline to the open water is the one of the most common, direct causes of fatalities in the cave

Sheck Exley’s book Basic Cave Diving: A Blueprint of Survival laid the foundation of safer cave diving.

environment. Though most cave sites seem benign—characterized by crystal-clear water and serene surroundings—looks can be deceiving. Disturbed sediments can quickly reduce visibility and greatly compromise the ability of dive teams that have failed to install a continuous guideline to the open water to safely exit the overhead. However, if a dive team has installed a guideline, even a complete loss of visibility can be effectively managed. Under such conditions, all a dive team would have to do is follow the guideline to the open water basin, whereupon they would make a safe ascent to the surface.

Many open water divers have little or no experience running a guideline; many have never even seen a cave diving reel. Any divers tempted to enter an overhead without a guideline would do well to remember that they are intentionally placing themselves in harm’s way by dramatically increasing the risks of their dive. Every year, divers lose their lives by failing to run a guideline. The most tragic aspect of this loss is that it is unnecessary. Running a guideline is very simple and it is a task well worth the effort.

To take advantage of the safety margins offered by a guideline, divers should practice with a reel and seek to cultivate a number of valuable techniques. With a little persistence, divers can easily overcome their initial difficulties and significantly enhance the safety of not only themselves but their team members as well.

Two-thirds rule

Diving in an overhead environment requires that divers maintain a sufficient volume of gas that enables them to exit from their farthest point of penetration. Furthermore, in the event of a catastrophic gas loss, divers must ensure that they have sufficient gas reserves to supply a team member with the gas needed to exit the overhead. Ignoring this policy is another reason for overhead fatalities. Cave divers instituted the “rule of thirds” to meet these requirements: one-third for penetration, one-third for exiting, and one-third for emergencies. Under this rule, divers penetrate into an overhead area while using no more than one-third of their available gas supply. The first team member to reach

Maintaining a continuous guideline is one of the easiest ways to increase safety during any cave dive.

PHOTO PETR POLACH

the one-third limit terminates the dive. During the exit, divers may then exhaust another onethird of their available volume. This form of gas management allows a remaining one-third to be available in the event a team member experiences a loss of gas, or some problem that delays the exit. The gas management section of Deep Into Cave Diving contains more specific information concerning the logistics of managing gas.

Divers entering the overhead who fail to reserve two-thirds of their starting volume for exiting risk having an insufficient reserve volume. Open water divers typically have little practice with this level of gas management and historically run into problems when venturing into the cave environment. Other divers may intend to follow good gas management practices but find that limited experience or inattention can result in accidental gas violations. Even divers with some overhead experience have occasionally violated this important gas rule, not to mention very seasoned cave divers who become lazy, overconfident, or careless and violate their gas reserves. Regardless of experience, violating the thirds rule creates a serious safety issue. Any time divers violate this rule, they unnecessarily place not only themselves but their team in harm’s way.

Excessive depths

Deeper diving creates a variety of risks for divers of all experience levels and is another common reason for fatalities in the overhead. Limiting new divers’ depth allows them to gain experience in more benign shallow water. It is for this reason that new open water divers are urged to remain in the 18 m/60 ft range while more experienced divers are encouraged to approach the 30 m/100 ft range. The maximum limit for the recreational sport diver is 40 m/130 ft.

It is important to note that as divers venture into deeper water, a number of variables will begin to increase the risk of the dive. For example, around 30 m/100 ft, divers will consume roughly twice the volume of gas that they consumed at 10 m/30 ft. This increased gas consumption becomes an even greater issue in an overhead environment, where gas management is critical. Under the thirds rule, only one-third of a diver’s gas is available for pene-

tration. Increased depths then further reduce a diver’s available time. Furthermore, other factors such as narcosis, gas density, and oxygen toxicity—and somewhat less likely factors, such as deep-water blackout—can combine to increase the risk of deeper dives. Even for veteran divers, deeper depths produce elevated risk, but with special training and equipment, divers can noticeably reduce some of the risk. However, deeper diving remains a statistically risky proposition and, unfortunately, continues to be a common cause of fatalities in the cave environment.

Lack of training

Divers entering new environments, let alone overhead environments, will often encounter unknown risks. In new surroundings, all divers, regardless of experience, undergo an acclimatization period allowing them to become more aware of their surroundings. By illustrating the many unseen risks that different environments present, training courses educate divers and help them develop skills and strategies for effectively managing risk. Divers operating without this knowledge often violate common rules for safe diving. The underlying cause of these violations is frequently the diver’s lack of understanding, indicating that diving beyond one’s level of training and experience remains the most avoidable risk in overhead diving.

Insufficient lighting

wDivers venturing into an overhead environment should possess at least three light sources. In cavern diving, where divers remain in the daylight zone, sunlight can be counted as one light source. Cavern divers, then, need only carry two lights. Insufficient light, like insufficient training, was not part of Sheck Exley’s original risk categories. To be sure, the loss of light will delay a diver’s exit, increase the risk of buddy separation, and generally contribute to the stress of the dive. However, if divers maintain a continuous guideline, follow the rule of thirds for gas management, and dive within acceptable depth limits, a total loss of light should not present any insurmountable difficulties for trained overhead divers.

Cave divers should remember that the rule of thirds is fairly aggressive, and many scenarios will require a more conervative approach to gas planning.

PHOTO KIRILL EGOROV

Failure to carry adequate lighting is most consistently a problem for open water divers who are not acquainted with the need for redundant lighting. Historically, open water divers have entered overhead environments with little or no reserve lighting. Sometimes, a team of open water divers will enter the overhead with only one or two lights. A failure of just one light, or a separation of the team, can easily lead to misdirection and a fatality. Cavern divers must remember that a total loss of light can test even a certified cave diver’s skills. Redundant lighting must remain a mainstay in overhead divers’ equipment.

FATALITIES IN TRAINED DIVERS

The first part of this article discussed the chief causes of cave fatalities as they relate to the general diving community. These five rules of accident analysis represent the most common mistakes divers make in the overhead. To reiterate, these are: training, guideline, gas, depth, and lights.

In contrast to divers from the general community with no cave training, certified cave divers are trained in the dangers of overhead diving. Cave training, however, does not eliminate all risks of diving in an overhead; it only educates divers to the intrinsic risks and perhaps helps them to properly manage these when they encounter them.

A careful study of accident records reveals that the majority of certified cave diver fatalities fall into three categories. These categories underscore elevated levels of risk when trained cave divers decide to violate these guidelines.

Diving to excessive depth

A primary cause of death among trained cave divers is diving to excessive depths. Deep diving introduces many new risks that can quickly overwhelm even the well-trained cave diver. Factors that contribute to elevated levels of risk here include narcosis, increased gas consumption, decompression sickness, and oxygen toxicity. Divers can reduce most of these risks by making different gas choices, undertaking proper training, and gaining sufficient experience. However, it takes a great deal of time and dedication to refine the techniques necessary to markedly reduce one’s risk at greater depth. Deep diving is well beyond the comfort zone of the new cave diver.

The importance of the guideline

Failure to run a continuous guideline to open water is another common reason for fatalities among certified cave divers. Despite their training, some cave divers ignore the risk of diving without a continuous guideline. While it may seem simple to navigate a given area without a guideline, any number of factors can greatly increase the difficulty of this task. When divers venture away from a continuous line, they surrender an invaluable safety factor and, consequently, increase their risk. Reductions in visibility, momentary confusion, high levels of stress, and equipment failure are just a few of the many reasons for maintaining a continuous guideline. Appearances are often deceiving; cave divers can easily make small errors in judgment that could leave them away from the line with little or no concept of the exit direction. The additional time it takes to maintain a continuous guideline is a small price to pay for the safety margin it provides.

Rethinking accident analysis

As discussed above, the evaluation of cave diving risk began nearly two decades ago with Sheck Exley’s Basic Cave Diving: A Blueprint for Survival. To pretend that these early studies provide us with a comprehensive account of modern-day risk is problematic. Changes in the cave diver population, in training regimens, in equipment advancements, and in cave divers in general raise troubling questions regarding the completeness of this early data. Nonetheless, it is likely that the primary categories—or causes—identified by Exley as being responsible for most cave diving fatalities (training, guideline, gas supply, depth, and lights) partially overlap, if not entirely coincide, with those of today.

“Historically speaking, many of the advances made in cave diving were the result of cave divers being meticulous in their analyses of fatalities.

Violation of one-third rule

Failure to maintain two-thirds of their gas volume for exit is yet another common reason for the death of certified cave divers. When cave divers choose to violate the rule of thirds, they compromise one of their most important safety margins. Once their reserve gas supply is compromised, it cannot be reclaimed. Divers sometimes develop a false sense of security and assume that several or even hundreds of successful dives indicate that the risk of gas failure is not a serious one. While it is true that most dives are uneventful and that divers rarely need this reserve volume, it is also true that, in the unlikely event that there is an emergency, failure to reserve adequate gas can easily lead to fatalities. Violating the rule of thirds seriously jeopardizes the entire team. Any members of a dive team that violate this rule endanger not only themselves but also every other member of the team.

Historically speaking, many of the advances made in cave diving were the result of cave divers being meticulous in their analyses of fatalities. However, since Exley’s A Blueprint for Survival, little has been done to document and appraise relevant new data that would contribute to forming an accurate representation of contemporary cave diving risk. This lapse of interest in accident analysis raises important safety issues, as it is precisely such data that is often used to generate training curricula.

Accident analysis has been critical in the development of cave diver training. As a result of such analysis, risks associated with the average (not cave-trained) diver entering a cave and those associated with cave divers entering a cave became carefully delineated.

Exley’s primary risk factors included the following:

• Lack of continuous guideline

• Failure to reserve two-thirds of gas supply for exit

• Diving to excess depth

In 1984, training and lights were added to this list to highlight the risk associated with

Cave divers are going deeper and deeper every year. The only way to do this reasonably safely is to use appropriate highcontent helium mixes.

PHOTO KIRILL EGOROV

While high-tech gear such as DPVs and CCRs enable divers to push the boundaries of what is possible, they also introduces unique risks and challenges.

untrained divers entering caves and to establish the need for sufficient lighting (primarily an issue of being untrained for cave diving). With these additions, the traditional risk categories were established and were taught in the following order:

• Lack of cave training

• Lack of continuous guideline

• Failure to reserve two-thirds of gas supply for exit

• Diving to excess depth

• Diving without sufficient lighting (i.e., at least one primary light and two reserve lights)

For trained cave divers, however, these risk categories are not only fewer in number but also ordered differently:

• Diving to excessive depth

• Lack of a continuous guideline

• Failure to reserve two-thirds of gas supply for exit

Though these categories effectively establish primary risk factors, they are far from exhaustive. Left alone, they create the illusion of well-defined risk. Whatever the degree of statistical precision achieved by the original analysis, today, the accuracy of these early results needs to be reassessed from the standpoint of a changed landscape where diving popularity, advances in technology, and effectiveness of risk factor education have evolved. Consider, for example, the not-too-distant past when cave divers could claim that there was not a single fatality among properly trained cave divers; today this is hardly the case. What accounts for this changing landscape?

Even though factors such as the huge increase in the cave diving population skew these numbers, this increase does not account for the rise in fatalities among trained cave divers, especially when reviewing the details of these fatalities. What seems to be at the core of the problem is that cave training seems to have lost its original rigor. Actually, this is a small part of a larger problem: a noticeable decline in the gen-

PHOTO KIRILL EGOROV

eral quality of diver training. Many have noticed the general decline of diving skills in the dive community, stretching from open water instructors with weak skills to poorly trained students. Nonetheless, the demanding nature of technical diving makes this loosening of standards and the resultant decline in diver skill particularly problematic.

New tools

Technological advances have also served to call into question the exhaustiveness and/or current value of the original risk assessment. According to the traditional risk categories, deep diving is the greatest cause of death among certified cave divers and, therefore by extension, the greatest source of risk. However, relatively few cave diving fatalities have occurred when divers have used sensible helium-based gas mixtures, meaning that, unless one examines the role of air diving in deep cave diving fatalities, to assess risk on the basis of the traditional model would be suspect at best.

Unquestionably, deep diving has its own distinct set of risks, e.g., increased time pressure, more rapid gas consumption, and risks related to decompression. However, promoting the view that deep diving is inherently responsible for most of these fatalities only serves to mask the true risk associated with deep diving—namely, the use of air. Understanding the role of air diving in deep cave diving fatalities would most likely have impacted the history of deep air diving and softened the odd resistance the community has to reasonable breathing mixtures.

An additional factor that was not included in initial accident analysis is the wider availability and popularity of rebreathers and DPVs. Over the years, scooters and rebreathers of different types gained tremendous popularity amongst cave divers. While these tools may provide incredible opportunities for well-prepared, experienced, and disciplined divers, the same tools may become deadly if used without proper understanding, planning, and training. As with any complex device, DPVs and rebreathers can and will fail and, in this case, divers will need a solid

set of open-circuit skills and a sufficient amount of gas to survive.

Further eroding the ability to make educated choices using the traditional assessment of risk as a guideline is the fact that these risk factors are no longer tracked with any degree of statistical precision. As a sign of this climate, some diving leaders have proposed adding solo diving to the list of risk factors. While solo diving has certain risks and is generally not recommended, without evidence, arbitrarily adding another risk category will only serve to distort the accuracy of risk determinations.

Nonetheless, the traditional risk categories undoubtedly provide divers with good general information and, for that reason, can be highly instructive. However, divers should be aware of and consider the limitations of these categories before they embrace them as sufficient grounds for action.

Personal level of comfort

Though training is a central component of diving safety, without common sense and objective self-regard, training can be nearly meaningless. Far too many divers see a certification card as insurance against risk, when it is really only a license to learn beyond the direct supervision of an instructor. During training, divers should gain

an appreciation for the risk involved and proper management of common problems. However, following training, certified divers must remain sensible regarding the inherent risks of a particular dive, choosing not to participate in dives that stand to tax their level of comfort and personal ability. Proper training is responsible for providing divers with an appreciation of the true risk of a given activity; it is the responsibility of certified divers to use that information to evaluate their preparedness for a particular dive.

Diving beyond the range of the gas

Breathing inappropriate mixtures is a common cause of death for technical divers. This has led to a great deal of attention to why divers accidentally breathe the wrong decompression mixture at depth (e.g., accidentally breathing oxygen instead of nitrox) and, as a result, convulse and drown. These errors seem to nearly always relate to poor tank marking and to ineffective gas switching procedures. However, divers also make unwise decisions when planning the gas mix they will use for a given exposure. For example, divers routinely dive deeper than 30 m/100 ft on air (a known narcotic gas) and with excessively high pO2s (greater than 1.4 while working), thereby exposing themselves and their team members to unreasonable risk.

PHOTO KIRILL EGOROV

Divers descending towards the deep section of Glavash Spring in Croatia.

Divers are typically free to make their own choices about breathing mixtures; however, due to the needless level of risk involved, choosing to dive gases that exceed a pO2 of 1.4 and an equivalent narcotic depth (END) of 30 m/100 ft demonstrates both a lack of sound judgment and great irresponsibility.

Improper or insufficient equipment

The most obvious case of improper equipment use involves individuals diving in an environment without the necessary safety equipment. Many fatalities point to the need for proper equipment, and divers that ignore this requirement place themselves at much greater risk. Cave diving is not an activity that permits equipment to be safely cobbled together from odd pieces. Proper cave diving requires divers to make an investment in their safety, to not accept substandard equipment, and to not allow themselves to be lured into environments without the right tools for the task at hand.

However, cave diving is as much about having the right attitude as it is about carrying the right equipment. To have one without the other can lead divers into dangerous waters. Many subtle encouragements to follow dubious diving practices exist, as the apparent success of such practices can lull divers into a false sense

of security. Furthermore, divers are resistant to changing commonly accepted practices, regardless of their actual track record. Divers that wish to maximize their fun and safety while enabling maximum performance must carefully choose their mentors and their dive buddies. Common-sense practices are sometimes anything but common.

Accident analysis

While there is a need for further improvements in accident data tracking and analysis, the information gleaned from Sheck Exley set the boundary stones not only for cave accident analysis but also for cave training. Though it is imperative that these early findings be constantly re-evaluated from within the context of emergent technology (e.g., the ready availability of helium as a breathing gas), revisiting the past nonetheless offers divers clues on how best not to repeat it.

NEXT TIME: ECOLOGY, CONSERVATION AND LANDOWNER RELATIONS

Sheck Exley and Jim Bowden after a dive in Zacaton, Mexico.

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