Diving In A Overhead Environment

by Bruce Konefe

If you had asked me eight or nine years ago to venture inside a submerged cavern or shipwreck I would have thought you where crazy. However, nowadays you’d get a completely answer: “Where and when do we leave?”

After logging a lot of dives and taking plenty of courses I now feel comfortable entering these types of environment. Having said that, this style of diving is not for your average recreational diver. The dives take a lot of preparation and planning in order to ensure personal safety.

Participants need to work on their skills and maintain regular proficiency in their application, since there is little or no room, for error once you are inside these confined, and more than likely, dark spaces.

Once inside a wreck or cave, the risk factors jump dramatically; loss of visibility is a common factor, either from bubbles breaking up ceiling silt or from being disturbed by fin action.

I have been a mere three meters inside wrecks and when I looked back the visibility had been cut down by half. An important skill taught in cavern and technical wreck diving courses is utilizing different styles of fin kicks to minimize the disturbance of any silt.

Accident Analysis

Cave and wreck divers have developed an acronym for accident analysis and contingency planning, T. G. A. D. L. One interpretation would be “Thank God All Divers Live“, however; its real meaning is to describe important traits of good wreck diving practices.

• Thank = Training
• God = Guidelines
• All = Air or Gas supply
• Divers = Depth limits
• Live = Lights

Training and Experience

About 95% of fatalities in cave systems come from divers with out proper training and 73% of accidents during wreck diving occurred when divers enter wrecks without the aid of a guideline. For fatalities that occurred outside the wreck, 43% were attributed to ‘out of gas situations‘.

Guidelines

In an overhead environments, the lack of a guideline is the single greatest cause for fatalities; any time you enter a wreck or cave a guideline should be considered as your extra ‘buddy’. Training in the use of these, and reels, are both key elements of cave and wreck diver training.

Air or Gas Supply

This is much more than ‘just watching a pressure gauge’.

In technical, cave and wreck diving, we typically operate under the ‘Rule of Thirds’. This means the diver uses 1/3 of their gas on the outward stage of the dive, 1/3 for the return journey leaving, 1/3 in reserve.

Many people think this may be to conservative but in my opinion, and I’m sure many others its better to be safe than sorry. Depth, combined with inexperience and/or poor planning can also be very unforgiving. Most divers know that gas depletes more rapidly at depth. Imagine how fast it goes in a stressful situation such as an entanglement inside a wreck!

Narcosis could also be an increasing factor in situations where incorrect gas mixtures are used. Oxygen toxicity is a possibility on improperly planned dives that fail to take into account the extra workload involved in a penetration dive.

Lights

Be prepared for low visibility and loss of ambient light. For non-penetration dives, a single light source may be sufficient, but for actual penetration the diver must carry a minimum of two extra backup lights. But it doesn’t end there, there are specific rules for brightness, burn duration and configuration that also need to be considered, and should be included in any training course. Thailand has lots of wrecks and freshwater cave systems worth exploring.

Be smart and get proper training then build up your experience slowly. Remember, training alone only provides you the tools. Experience requires repetition and a slow process of increasing the limits of your diving abilities.

ABOUT THE AUTHOR

Bruce Konefe works for American Nitrox Divers International, and has lived in Thailand for more than 14 years. He is an instructor trainer who now teaches at only the highest levels of technical diving, and has helped design both cave diving courses and hyperbaric chamber medical courses for the agency. His career has taken him around the world, including to Australia, Canada, Dubai and the United States. He has trained military divers in both the Thailand and the Philippines, and was on the team which first dived on the IJN Yamashiro, a 39,000-ton Japanese battleship sunk on 25 October 1944 in the Second World War battle of Surigao Strait.