When diving into caves, wrecks or under ice divers are introduced to a number of hazards not associated with open water diving. Some of these are easily managed. Others may be life threatening. General hazards include total darkness, loss of visibility, increased potential for confusion, unexpected currents, cave ins, restrictions, depths, unknown distances, mazes, turbidity/silting, current, sharp surfaces and projections, collapse, debris slides, restrictions minor and major, depth, distance, time.
Darkness
Absolutely no light penetrates most cave systems and one of the first things to realize is that the darkness is total. Not the slightest bit of light penetrates the solid rock ceiling, there are no stars and there is no moon. In caves the prospect of being lost in the dark can have chilling effects. When lost or when loosing ones light stress levels typically climb. Don’t let panic skyrocket. Cave diving requires disciplined self control to function correctly. This discipline must be learned and practiced.
Being lost
Several common factors, or combinations of factors, contribute to the possibility of a cave diver becoming lost. Becoming lost is a threat on any cave dive. Caves frequently present divers with a number of mazes, dead ends and multiple levels of formation. Accidentally wandering into an unintended passageway can result in dive partners becoming lost. In fact, one of the leading causes of cave fatalities is the failure to follow a continuous guide line and set jump lines that lead all the way back to the surface. Guide lines are the diver’s path back to the entrance, they are a cave divers life line. Guide lines offer life insurance by providing cave divers with a marked path to the surface. It is imperative to keep an eye on these lines at all times. When visibility is good you should swim close to the line at all times so the line can be easily located. It is important not to stray too close to the line neither since the possibility of becoming entangled in it increases. Entanglements can become killers because they can result in broken or loosened lines. When limited visibility conditions occur, one must stay closer to the line. The best technique to stay in touch with the line once visibility has deteriorated is to swim with your thumb and forefinger forming a ring and looped over the line.
Visibility
In explored caves it is common to find permanent lines with arrows pointing toward the nearest route to the surface. Turbidity is caused by stirring up debris on the cave floor due to poor swimming techniques or due to percolation when exhaust bubbles hit the ceiling. It can reduce visibility to zero within seconds. From both a dive safety standpoint and an environmental point of view with cave conservation in mind, it is important for you not to stir up the bottom of a cave. Tannic acid is the color of soil and can be washed into the water by rivers or rain. It has the color of tea or coffee with the same visibility characteristics. A Halocline is the interface of fresh and salt water and when mixed produces zero visibility.
Water flow
Current in caves can range from none to mild and even to severe. New cave divers are often intimidated by these currents. They tend to overwork and become tired quickly. By carefully employing proven techniques, the work may be reduced to a less demanding level. The best way to beat the current comes with learning to read the cave. Areas where the surface is smooth have been polished by the flowing water. So, you should look for jagged and pitted surfaces. They exist where the current is weakest. Current can also be out flowing or in flowing. Sometimes caves divers may encounter passageways featuring flows differing in direction from the passage currently being explored.
Cave or wreck collapse
Cave-ins ( collapses ) are rarely encountered in cave diving. Water pressure acts as a support and stabilizes submerged tunnels. It is only when water levels drop that the possibility of collapse exists. Occasionally, in some caves a small portion of the cave structure will fall in.
Debris
During floods, debris builds up in the down slopes of cave openings and in the runs. When the water table drops, additional debris is blown out of various passageways and is deposited on the cave floor. As these strictures extend toward the surface, more debris builds up in the run. At some point, the volume of these deposits reaches a point where gravity causes it to slide back into the cave. The result, in both cases, is an instantaneous loss of visibility. In fact, on one of these occasions visibility can be so obscured that it would proof impossible to get out if divers hadn’t had the mandatory foresight to install guide lines beginning at the cave opening. In some situations, it is possible that the cave opening actually becomes blocked.
Restrictions
Restrictions are choke points where access is reduced. They can be either minor or major. A minor restriction is a slight narrowing which, although restricted, still allows two divers to pass through it not side by side or on top of each other but in a single file following one another. A major restriction, on the other hand, only allows one diver to pass if the equipment is to be taken off and pushed through the restriction. As a rule of thumb the equipment is never taken off due to potential problems with buoyancy, damage, entanglement and cave conservation. If the need arises to pass through a mayor restriction gear configuration such as sidemount or no-mount have to be implemented. Obviously, the risk associated with a major restriction involves becoming stuck. When entering restricted areas be careful to evaluate the best passage route while also concentrating on relaxed breathing. If stuck, exhale some air and slowly maneuver your body and simply dislodge your self. Do not try to “ power through ” restrictions. You may become severely wedged. We can’t stress it hard enough. Take it very easy when swimming in tight spots. It is very easy to tear a BC bladder or damage your gear. Again, learn to read the cave and avoid abrasive and protruding surfaces.
Depth
Depth in caves can be very deceptive because you have a roof over your head and a floor under your feet. Don’t forget to monitor depth regularly. Depth increases gas consumption, the risk of nitrogen narcosis arises, can cause oxygen toxicity and produces a greater decompression obligation. This is why many cave divers use Normoxic or Hypoxic Trimix mixtures for deep cave exploration.
Distance
When a problem arises we realize it’s a long way back. Distance, in this instance, may produce additional time-pressure stress. In worst case scenarios, your gas supply may be compromised if one team member experiences gas failure. Training and awareness, combined with careful planning, will enable you to deal with the hazard of distance. The ceiling over your head prevents direct access to the surface. This is why highly reliable equipment combined with redundancy is used for cave diving. Changes in respiratory patterns, such as response to mental and physical stress will also increase gas consumption. When divers slow their pace, gas consumption is reduced. Never forget that your exit speed must match your entrance pace. You must cover the same amount of ground in the same time “coming out” as “going in” to insure you won’t run out of gas.
Air and team management
Since dive teams are obviously composed of individuals, a “ team gas management ” rule must be established. This rule incorporates all the factors involving individual considerations with another dimension. This dimension is created by people working together. When diving alone, dive techniques and gas management are different as if diving as a team member of a dive team.
The size of the dive team will dictate effective gas management. Obviously a two person dive team is the most efficient from a dive performance standpoint. It needs less communication and requires less choreography. Both divers know where their partner is. Swim pace is easier to regulate. A small team reduces the level of environmental management needed. For example, silting is just one of many factors that’s easier to anticipate and prevent.
However, there are strong arguments to support the advantages of a three person dive team. The group gas supply can go much further when shared between three people. Two people are usually better able to rescue an individual in trouble. Irregardless, the gas plan to be used must be developed from a swimming based surface rate ( vs. a resting rate ). It must be fine tuned by adjusting anticipated gas consumption against the environmental factors you expect to encounter. Experience has taught us this method is almost always totally accurate for planning dives involving a lot of swimming. To do this right, all dive team members must know their individual RMV’s.
Even with proper gas matching, it is still imperative that all dives remain within normal parameters for these rules to work. When conducting cave diving on your own, or with new team members, it is advisable to add a couple of hundred psig / dozen bars to any turn around point and turn around earlier. This practice should be continued until divers have sufficient experience to develop the discipline to function normally under stress.
Running out of air
By taking corrective actions with gas supply problems, for example, before things escalate, divers can begin sharing gas before the diver with the problem actually runs out completely. This is good stress management. It allows the distressed diver to use his or her own gas whenever a restricted or hazardous point in the dive is reached and share air in the long, unobstructed passages. Once any member of the dive team is using a back up regulator, the dive should be terminated. All divers should begin their pre-planned exits.