CAVE DIVING NAVIGATION & TECHNIQUE

Cave diving is a surprisingly safe activity when done properly and with the right amount of training, practice, and skills.

Caves offer more predictable and stable milieus without a lot of the environmental variables associated with diving in the ocean. But, going into a cave lacking solid navigation skills and proper diving techniques can quickly change the situation from benign to dangerous. Let’s review cave navigation protocols and define what we mean when we talk about good technique in cave diving.

Divers must be extremely careful when using arrows to mark navigational decisions.

cave diving has evolved, so have the methods used to mark the line—a critical navigational aid. In the early years, divers used items such as colored ribbons and duct tape tabs to mark the exit. Some divers even marked the line with different-sized knots to reference the exit. Today, the most common marker is the line arrow: an isosceles triangle that should point in the direction of the exit. The line arrow is popular because it can be easily affixed to the line, remains securely attached where it is placed, and, even in zero visibility, clearly marks the direction of the exit.

Divers also use non-directional markers on the line. Originally, these markers were clothespins, but this type of marker has proved to be unstable, can easily fall from the line, or can be accidentally moved. Today, “cookies” are a more common non-directional marker. This circular shape provides a secure way for divers to mark their position with information relevant to their team but avoids the potential confusion for other dive teams with misleading directional arrows.

Navigating multiple exits

Multiple exits can increase the complexity of a dive and lead to confusion. When diving in a cave system with multiple exits, it is important that divers remain individually cognizant of the exit and never rely on line marker placement.

For instance, though line arrows should always point in the direction of the nearest exit, sometimes this exit is not the one sought by a given team. This is because the nearest exit may not be the one the team used to enter the cave system or the one that guarantees a continuous guideline out of the cave system. In fact, the marked exit might require divers to navigate beyond multiple gaps in the line to reach the intended exit. Inexperienced cave divers should limit their dives to simple penetrations and avoid the potential confusion of multiple exits.

This circumstance highlights the utility of non-directional markers. A team may place a

Ascookie on the exit side of a T, indicating their exit direction without confusing the exit for other dive teams.

Traverse

A traverse entails entering from one site and exiting at another distinctly different site. For example, divers can enter a cave through one sinkhole, travel through a cave passage, and exit at another location (usually another sinkhole).

Given that a traverse involves more than one entrance, and that divers may enter from either site, line marker placement and/or the shortest exit route can cause confusion. During a traverse, cave divers entering from a spring or sinkhole and continuing in the direction of another sinkhole may find that the line arrows will start to point away from their exit direction. This happens because, as a diver reaches the midpoint between the two exits, line arrows will generally begin to point toward whichever exit is closer. In other words, caves with multiple exits usually have arrows that reverse at the halfway point.

New divers should understand that an arrow pointing into the cave may be the result of several factors. It may indeed be that the diver has reached a halfway point between two exits; however, it could also be that the arrow was incorrectly installed, or even installed by a team diving from another entrance. Therefore, dive teams should never rely on markers placed by other divers, as these can provide incorrect information. Even if divers feel convinced that certain line arrows represent the true midpoint between two exits, they should terminate their dive upon reaching their one-third limit. Even though a team may be able to reach the end of the line during a traverse from one sinkhole to another (indicating that the second entrance is nearby), there is no guarantee that they can get to the open water from this new position.

Without a guideline installed to the open water, they may be unable to locate the surface. If divers violate thirds in order to reach this second exit but are unable to locate the surface, they may not have sufficient gas to manage a return trip. A dive in which a dive team relies on secondhand information to complete a traverse, and violates their gas rules to do so, is one that flirts with disaster. Information about negotiating these restrictions can be found in the Dive Planning article later in the series.

A permanent intersection, well-marked with arrows in Peacock Springs, Florida (USA).

Bridging the gap

When a guideline intersects with another exit, such as a sinkhole, the line will generally stop prior to reaching the daylight zone. Permanent lines may not run through basins because they can encourage open water divers to enter the cave.

In this case, the properly trained cave diver would install a temporary line that would join the two ends of the line. Bridging the distance between the ends of two lines is called a gap. This separation between permanent lines introduced by sinkholes is another of the associated risks relevant to multiple exits. As mentioned above, divers can become lost very close to the exit and may be unable to find their way to the open water.

Indeed, permanent line placement designed to discourage untrained divers from entering the cave has been responsible for stranding careless cave divers several hundred feet from the exit, unable to find their way out. In this regard, it is often a difficult task to balance the desire to protect people from themselves with the need to simplify cave navigation. Regardless of divers’ personal views on this matter, in the end, cave divers are individually responsible not only for their own navigation in potentially difficult regions but also for their dive practice as a whole; they should always dive comfortably within their limits.

Spring flow

Caves vary considerably with respect to general structure, flow conditions, and sediments. While all of these factors can impact diver safety and comfort, variations in spring flow can require careful planning.

Spring flow can complicate a number of elements: gas management, exertion, stress, travel time, visibility, and scooter burn time. For example, divers entering a cave where water outflow is strong will find that penetration will be more difficult and will require additional time and energy. In turn, spring outflow will facilitate a quick exit with reduced gas consumption and less effort required.

Conversely, a siphon (water flows into the cave) will facilitate diver penetration but will require greater effort and gas consumption to exit. In diving siphons, normal gas rules are inadequate and are replaced by guidelines that are designed to reduce the risk of such dives. Nonetheless, it is important to bear in mind that many of these rules are somewhat arbitrary and of limited benefit. Only very advanced divers should dive into siphons, as inflowing water can both complicate dive planning and compromise team safety.

Similar problems can surface when diving in areas with multiple exits, even without diver awareness of the associated risks. For example, divers undertaking a traverse in caves with notable flow will be subject to outflow (spring) conditions when entering from one entrance and to inflow (siphon) conditions when entering from the other. Therefore, divers planning to establish a connection and dive a traverse would find themselves obligated to two different sets of gas management rules and to a range of potential complications. Generally speaking, when diving in areas with multiple exits, teams should travel against the current to avoid dangerous siphons and complicated gas rules.

Siphons

Though there are no hard-and-fast gas rules with respect to diving siphons, doing so nonetheless requires dive teams to reserve a greater quantity of available gas.

It is difficult to establish credible gas rules for diving siphons since flow conditions vary from one cave to the next. Historically, individuals have recommended using no more than 1/6 of their gas supply (as opposed to 1/3) when penetrating siphons. However, such a rule is arbitrary, as it does not allow for the variability of conditions nor to the different levels of spring flow.

Such recommendations should only be taken by divers as generic starting points, and divers should remain aware that, in most cases, gas rules of this kind will be modified as one’s dive experience and familiarity with equipment grows. In diving siphons, assessing one’s required gas supply is mostly an experience-based skill acquired over multiple shortrange diving ventures. Divers can undertake limited penetrations while using conservative gas management rules (such as the 1/6 rule) while they gain an appreciation for the amount of time and gas necessary to exit against the siphoning flow.

While working on a project, you may need project-specific equipment (scale bars, measuring tapes, etc.).

DPVs are a great tool in cave diving but should never be used without the proper training and preparation.

Divers must evaluate similar and even more complex practices when considering the use of a DPV in a siphoning cave. Of course, divers must be able to exit the cave in the event of a DPV failure. Additional considerations for diving siphons include placing safety bottles (bottles left for emergencies) and diving with additional DPVs that can be used in the event of an equipment failure. More complete information on planning dives of this nature is available in the Dive Planning article in this series.

Technique

Poor diving technique not only greatly increases divers’ stress but also reduces divers’ ability to manage emergency situations. Most emergencies are the cumulative effect of a series of trivial problems—usually issues resulting from poor diving technique and/or situational awareness. Divers with good buoyancy, proper trim, and an efficient equipment configuration are far less prone to unnecessary stress. These divers are also much better prepared to manage diving problems.

The words trim and buoyancy are sometimes used incorrectly to mean the same thing. Though related, these skills are two different elements of efficient diving, each requiring practice to master. Buoyancy refers to a diver’s ability to maintain a neutral position in the water while adjusting to weighting variations that result from changes introduced by gas consumption and compression of thermal insulation. Proper trim refers to a diver’s position (ideally somewhere near horizontal) in the water relative to the bottom. Once divers learn to balance trim and buoyancy, they will find that their swimming efforts and gas consumption will decrease, making their dives easier, more efficient, safer, and much more fun.

Good buoyancy control is a key aspect of any form of diving, but it is especially important in cave diving. Swimming in silt-laden areas with rock obstructions above divers’ heads requires finely-tuned buoyancy skills. Just as important, if not more so, is divers’ trim. Divers swimming along in a cave should be horizontal to the bottom so as to minimize the potential for stirring up sediments.

Poor trim would indicate that divers are not horizontal and that some part of their body (usually feet or knees) is either contacting the bottom or directing water toward the sediments. While good buoyancy control is usually indicative of divers’ levels of experience in the water, proper trim marks a mastery of diving efficiency.

Weighting

Divers demonstrating good trim move through the water in a horizontal position with their feet slightly elevated. Most divers (incorrectly) swim in a feet-down position using a kick that generates a downward thrust. This increases the surface area of the body seeking to move through the water as well as the energy required to propel it forward. This posture also directs additional thrust from divers’ fins toward the bottom, potentially disturbing sediment and reducing visibility. Swimming with poor trim can lead to reduced efficiency, increased effort, bad visibility from disturbed sediments, and a damaged diving environment. Therefore, proper trim can be an asset for good cave divers, but improper trim can cause issues that should be of concern for divers in any underwater environment.

Certain buoyancy compensator (BC) designs can actually impede divers’ abilities to achieve proper trim. For example, BCs with restrictive bands can promote gas trapping and increase drag by generating turbulent flow around the diver. Trapped gas pockets can create unequal pockets of lift, throwing divers off balance. Furthermore, traditional jacket-style BCs generally lift the upper portion of the body, forcing the legs downward and making it even more difficult to remain horizontal. Though prac- ticed divers may be able to overcome this shortcoming, back-mounted BCs facilitate proper trim.

Conventional open water weighting systems—by positioning the bulk of a diver’s weight around the waist—tend to promote a feet-down swimming position and impact proper trim. Cave divers usually avoid this by wearing heavier double tanks. However, all divers (including recreational) would benefit from redistributing this weight and establishing proper trim. Divers can accomplish this by using a steel backplate, a weight behind the backplate (such as a V-weight for doubles), or a weight on the back of a single tank. Steel cylinders can also help divers limit the need for additional weight.

Clearly, divers need sufficient weight to maintain continuous submersion below the surface despite changes in buoyancy (initiated by factors such as gas consumption). Divers must also avoid over-weighting themselves, which is a far more common problem.

It is very important that divers evaluate their buoyancy to ensure that they are properly weighted. When properly weighted, divers should be able to hold their position in the water at 3 m/10 ft (for safety/decompression purposes) with nearly empty tanks. If under-weighted, divers could float to the surface in the event that an equipment failure caused a complete gas loss; if over-weighted, they would need more gas in their BCs, thereby increasing both their drag and the energy required to propel them forward. The effort of struggling against improper weighting alone can create enough stress to trigger an emergency.

It is difficult to exaggerate the value of proper weighting, good buoyancy control, and fine trim. In most cases, weaknesses in these areas go largely ignored but contribute to considerable levels of discomfort and stress. Failure to address these areas can easily be said to have led to countless accidents. Divers should seek to master these fundamentals and to maintain a close watch on anything that may impact them. Other excellent methods for improvement include asking others for critical advice and having another diver videotape their in-water performance.

Next time: Cave propulsion

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Precise and slow communications are key to team comfort and efficiency.