LIMITED VISIBILITY

Recreational scuba diving takes place around the world in all kinds of environments. The widely divergent water conditions—from crystal clear to dark and turbid—create significant variations in visibility.

Regardless of these varied settings, a wellrounded diver should be able to adjust to the underwater environment by using appropriate techniques and equipment to overcome visibility challenges. Some specific techniques can prevent reduced visibility; for example, divers can learn to position themselves, move with greater precision, or hold still in areas where sediment disturbance greatly impacts visibility.

In cases where visibility is limited from the start, such as during night dives or while exploring turbid waters, divers can use certain equipment or procedures to dive safely.

“The light supports effective communication over reasonable distance and/or during limited visibility dives while also greatly illuminating the area around divers even when the conditions are extremely dark.

The primary light facilitates team coherence in dark environments or in situations with limited visibility.

Diving in limited visibility can present unique challenges, including difficulty with navigation, risk of team separation, disorientation, and difficulty in controlling buoyancy and/ or ascent rate. The appropriate equipment and techniques address all of these conditions.

Equipment

GUE’s standard equipment configuration was initially developed for diving in areas with limited visibility. This standard configuration, therefore, provides a great start for most divers. For example, most GUE divers will use a high-intensity primary light for most or all of their diving activity. This light supports effective communication over reasonable distance and/or during limited visibility dives while also greatly illuminating the area around divers even when the conditions are extremely dark. These lights are also focusable, so they can be adjusted in waters that contain suspended particles. A tighter beam allows the diver to limit backscatter (which occurs when a light reflects off sediments) and increases communication abilities at great distances. Meanwhile, being able to de-focus the beam allows divers to get a better view of the surrounding environment. A lighthead that allows the diver to switch between a narrow and a wide beam offers the best of both worlds.

Primary lights

A GUE diver uses what is called a Goodman handle on their primary light. This offers the ability to use the light while leaving one’s hands free for other uses. This is accomplished with a light that sits on top of the diver’s hand, almost like a glove, and is supported by a grip nestled in the palm of the hand. The primary light battery should be at least sufficient to power the light beyond the anticipated duration of the dive—including possible extensions to the dive time—and also for limited use while on the surface. GUE divers normally prefer a light with approximately 50% more time than needed, although they might adjust this factor depending on the type of dive and the experience level of the divers involved. LED technology combined with advances in battery technology offers impressive light intensity with a relatively small lighthead over many hours.

Backup lights

Diving in reduced visibility environments also requires a secondary or backup light. These lights are typically smaller and have reduced light intensity, but they should still produce a reasonable amount of light. One can gauge the intensity of an acceptable backup light by testing their comfort in relevant environments while using only this light. If the light is not sufficient for comfort and communication, then divers should consider another option. Should problems arise with the primary dive light, divers can maintain reasonable visibility and communication with their team using a backup light. Divers should carry at least one backup light and store it in a convenient and secure location that reduces the risk of loss or entanglement—like the shoulder strap connecting the top and bottom of a diver’s backplate.

Reliability should be the main characteristic of a backup light. Other important features include a minimalist design with fewer failure points or possible water intrusion points. Turning the light on and off is usually accomplished by twisting the lighthead, a simple mechanism that reduces some of the complexity of switches. Backup lights should be powered by non-rechargeable batteries since they are designed with a long shelf life and provide a more reliable output when compared to rechargeable batteries, whose discharge has a tendency to decline over time, especially if not recharged regularly.

Small strobe lights can also be useful while diving in reduced visibility environments. In situations where it is important for the team to return to a specific point, strobes can be used to indicate the exit point or the ascent line; they can also make a diving buoy visible at the surface during night dives.

In situations with appropriate water clarity, chemical lights sticks (Cyalume) can also be used as markers.

Other light sources

Divers should verify that they can read all gauges in reduced visibility or dark environments. All instruments should be luminescent or use some form of self-illumination (backlight) so they can be read easily. Most gauges typically remain bright for a couple of minutes after being illuminated for a few seconds with a reasonably bright light, and the team can always refresh this illumination with their handheld lights. Bottom timers and dive computers normally have their own backlights, which makes their screen easily readable in a variety of conditions. Divers should practice with these instruments and ensure they do not set the gauges to have very high illumination during dives. Looking into a very bright gauge (or any other light) can be uncomfortable or even dangerous when the pupils are dilated because of the dark surroundings. This action also temporarily reduces divers’ ability to see around them, so using a very bright gauge will be a continual source of distraction, negatively affecting vision throughout the dive.

Other tools

A few other key pieces of equipment include a navigation line, navigation markers, a compass, and, for some dives, a navigation computer. A navigation line can be deployed from a reel or a spool, which is chosen based upon the amount of line needed and the intended use by the team. Use of reels and spools can be challenging in the beginning and lead to entanglement or team confusion due to task loading and increased stress. Divers should seek training to support use of these tools. Diligent training is critical for diving in overhead environments since they can pose additional risks. Some divers might use various line marking tools, such arrows and cookies, to mark areas or directions of travel. Compasses can also help divers ensure proper directions of travel, track their path, and return along the same or similar direction. These various tools might also be useful when used together with dive area maps. Finally, some divers might consider evolving technological support that allows divers to track one another as well as a boat or other point of entry. These tools are becoming more affordable and more reliable and will likely one day be as common as smartphone map navigation.

Surface light sources, like powerful boat lights, assist divers with navigation in dark or lowvisibility environments.

Procedures

Detailed dive planning, solid navigation skills, and adherence to team diving procedures (such as those advocated by GUE) greatly reduce the risks associated with diving in reduced visibility environments. When diving in such conditions, the following guidelines greatly enhance team capacity while also increasing safety and fun for all involved.

Team goals should be simple, realistic, and consider the capacity of individual team members as well as their experience in reduced visibility environments. The team should be careful to establish clear responsibilities for each team member, including their position in the team and the way the team will orient while diving. For example, will the team be in a single line or side by side? Knowing the formation ahead of time, as well as one’s place in this plan, will greatly reduce risk of confusion or loss of a team member. The team should also discuss the appropriate distance between team members, which is based upon the visibility and team member experience. Diving about one arm-length apart notably reduces risk of separation and makes communication much easier. Procedures for managing a possible team separation should also be made clear so that all members understand how they are expected to act if they are lost or should they notice a missing team member. Finally, all team members should be careful to avoid forcing or coercing fellow divers into activities that make them uncomfortable.

When a team member seems nervous about the visibility or suggests calling the dive because conditions appear to be worse than expected, the rest of the team needs to honor that person’s discomfort and avoid making any disparaging comments toward them.

All equipment should be well maintained and thoroughly checked during the pre-dive equipment procedures. Ideally, the team will be using a standard configuration so that all members are similarly configured; all equipment should be checked and its location verified, with differences between team members noted for everyone to consider. Diving in limited visibility conditions can notably increase stress, foster problems, and greatly complicate emergency situations. Therefore, divers should take extra care that their team members are aware of and can easily locate all useful equipment if needed.

Dive exposure plans should be adjusted in a conservative direction while considering depth, bottom time, and gas used. This is especially true while the team gains experience in challenging diving conditions. The increased risk of team separation and the complexity of performing a slow ascent or decompression stops in reduced visibility dictates avoidance of overly aggressive profiles while engaging in recreational diving.

Gas choices

Team members should also consider the choice of breathing gas during low visibility dives. Reduced visibility can encourage psychological stress, which may in turn influence respiration, leading to increased levels of carbon dioxide. Increased CO2 and heightened stress from re- duced visibility can further enhance the effects of gas narcosis, negatively affecting awareness. In these cases, divers should consider using a gas with helium, such as triox 30/30, as it reduces many of the above risk factors. Elevated stress during low visibility dives can also increase gas consumption and necessitate adjustment of planned turn pressure. Increased awareness and accurate gas tracking will allow the team to modify the dive plan before increased gas consumption becomes an uncontrolled risk.

Intensified current, increased boat traffic, cold water, and obstructions in the water are some other environmental factors that should be considered, as they enhance risk and increase stress levels, especially in a low visibility environment. Monitoring environmental conditions and maintaining awareness supports early detection of any developing problems in the environment.

Techniques

Navigation, communication, and control are three of the most important skills for diving in limited visibility environments. Divers should employ a combination of natural and compass navigation. Less experienced teams should avoid night diving in areas where they have no prior experience, or they should at least join divers with previous experience. Knowing the dive site and having good natural navigation references supports fun and safety during a night dive. As divers build experience, they can slowly expand the area they explore, allowing the team to become familiar with environmental references before moving further from the entry/exit point. The same guidelines apply while diving during the day in areas of limited visibility. The team should gradually expand the area explored, making sure they have adequate navigational references to safely return to the exit point.

Compass bearings, distance covered, course followed, and even a rough map of the most important landmarks can be noted to wetnotes, aiding the team in its navigation.

Communication

Diving in reduced visibility conditions also necessitates the use of clear and unambiguous communications among team members. Proper use of a diving light in both passive and active communication is important, as it might be difficult for team members to clearly see each other. Passive communication results from divers seeing the presence of the light from other team members, which helps to keep the team together. Active communication includes signals with the light such as “ok” by making a circular action with the light or “attention” by moving the light back and forth steadily, or even “emergency” by waiving the light more aggressively. Hand signals should be illuminated in a way that makes them visible, while at the same time assuring that the light beam doesn’t blind the rest of the team. Team members with weak or broken lights should be placed between other team members. Touch contact can even be used in very low visibility whereby a diver can hold the elbow of their team mate, keeping the team together and/or helping to guide confused divers.

Skills

Having precise control over one’s body while diving is a skill that is built over time and with practice. GUE training focuses heavily on developing these skills so that divers can move any part of their body in a precise and conscious way. Exceptional control may be rarely needed in most diving if divers remain in appropriate environments and dive within their limits. However, good control always supports a bet - ter diving experience including more fun and safety along the way. As dives become more complicated and environments become more challenging, a diver’s level of precision should likewise improve, and precision becomes progressively less optional. Being in control while underwater involves 1) a diver’s position in the water column adjusted by changes in buoyancy, 2) maintaining stability by learning to minimize unnecessary movement, and 3) moving efficiently through the water without disturbing sediments. Each of these aspects can greatly affect the way divers move through the water and usually have the greatest effect on the visibility immediately around a diving team. Many divers make the visibility somewhat or a lot worse due to inattention to these three aspects. Even divers with good stability, efficient propulsion, and solid buoyancy control can struggle in poor visibility given a lack of clear visual references. The disorientation can be especially prominent during a vertical ascent to the surface. In this case, divers often ascend too quickly or even go up and down as they rise too shallow and over-correct, sinking too deep. In aviation, an activity with many similarities to diving, pilots are trained to overcome these difficulties by focusing on the aircraft instruments, as their senses will most probably be mistaken. With practice, this tactic can help divers as well. Ascending slowly with planned stops or waypoints during the ascent can support the accurate reading of instruments while anticipating buoyancy changes and supporting a controlled ascent with no visual references.

Stress management

The equipment, procedures, and techniques divers use have a substantial impact on their comfort, not to mention the type of environment they will be able to safely explore. By developing a strong foundation of quality equipment standardized within the team, one can avoid confusion and simplify all diving activity. Meanwhile, appropriate procedures and techniques are a huge asset in managing a wide variety of environments. To some extent, all these aspects are somewhat refined by the environment explored. However, GUE has carefully chosen training and equipment that supports a vast array of diving environments with particular attention to enabling divers to manage more stress with less anxiety and more comfort. This is very true while diving in reduced visibility environments as well as a variety of both simple and challenging environments.

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 fulltime 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. Because of his strong interest in increasing dive safety through quality education, he also produces training videos for GUE.