It goes without saying that sooner or later even the best-laid dive plans go awry. And usually when you least expect it. But even when the worst occurs, a well trained diver can manage his new circumstances if he is conditioned to always have a contingency plan to implement. “Murphy’s Law” has an infinite series of disasters lurking for divers whatever environment they choose to explore: caves, rivers, quarries, deep walls, or even shallow reefs on drift dives. Let’s examine a few curve-balls that get tossed the way of these intrepid explorers.
Most scenarios will involve low or out of air situations or isolation from surface support. Low air crises are typically initiated by one or more of a combination of events that often involve entanglement, getting lost inside or outside the wreck, equipment failure, poor observation of gas management rules, or unpredictable natural catastrophes such as break-downs of the wreck structure itself. How the diver reacts to these types of stress may determine his ability to survive.
There are plenty of suggestions for generic guidelines in gas management that may involve various implementations of the cave diving community’s “rule of thirds” (one third of starting gas volumes for initial penetration, one third to come out on, and one third in reserve), or less conservative rules if no penetration or decompression ceiling is anticipated. Key to all gas volume planning is matching the plan to the diver with the highest breathing rate and the smallest volume of breathing gas carried by the team. This should allow a reasonable margin of safety in most circumstances.
Entanglements in fishing line, old nets, electrical wire, wreck debris etc. are a matter of routine for many divers. The assistance of a buddy diver can be invaluable in extricating a trapped diver but individual self-rescue should be the first order of priority. That includes an attitude of “defensive diving” and an awareness of one’s surroundings at all times. At least two sharp knives worn on the arm or chest area within easy reach should be standard gear. Many divers have found that carrying a pair of wire clippers capable of quickly cutting through such hazards are invaluable. Your macho-looking “broadsword” strapped to your calf won’t do you much good if you can’t reach it or if it isn’t sharp enough to do the job.
Most divers can easily cope with entanglements that snag them from the front, but can you deal with a wad of mono-filament hung in your valve manifold where you can’t see it? Familiarization with your own equipment is absolutely essential. You may have to remove it in a confined area to deal with the problem and then replace it. This can take time and throw your air consumption and bottom time calculations out the window. Self-control and smooth logical reactions to stress are survival tools not practiced enough by most divers.
Well, now you’ve managed to cut away the entanglement but in the process the wreck interior has silted out from your bubble stream and movements in the confined space. Your powerful dive light can only reflect a blinding backscatter of suspended particles rendering your vision to zero. One school of thought advocates “progressive penetration” whereby, at least theoretically, the diver “memorizes” the wreck interior by gradual excursions over many dives until the diver can effect an exit by touch and learned landmarks. I happen to think that this is a bit overly optimistic especially if you are four decks down inside the Andrea Doria, and some veteran wreck divers whom I greatly respect swear by this method. But after some forty years of professional diving and having wrecks cave-in on me, lights fail, and other dive teams silt-out rooms for me once too often, I’m a firm advocate of employing a reel with line to provide me a continuous pathway to the safety of the wreck’s exterior. One thing is for sure, you can’t start up to the surface until you get outside the wreck. You make the call on which method will provide the most reliable exit.
Almost all deep wrecks will call for planned decompression. Some divers elect to carry all necessary gas volumes for the dive itself and the decompression on themselves in the form of doubles or extra “stage tanks” reserved solely for ascent and hangs. Others plan to return to the anchor or ascent line and rendezvous with extra cylinders hung off at the first decom stop or supplied from hoses attached to large cylinders on the boat. Since most technical divers are using oxygen or nitrox mixtures for more efficient decompressions, it’s vital that these extra gas supplies can be located and accessed. That’s usually not a problem if ocean currents are not a factor or if the diver can guarantee his underwater navigation will return him to the ascent line.
However, if your dive buddy is named “Murphy”, you can count on getting disoriented due to reduced visibility and missing the up-line or simply getting blown off the wreck by a strong current. Even if you do everything perfectly, the boat itself could break free if its anchor line parts or breaks out of the wreck. That’s why the prudent diver will leave his decom tanks clipped into the wreck at the nearest point to his penetration entrance. If unexpected events delay his exit or make it impossible to return to the anchor line, he will still have the necessary gas supply to make a controlled ascent and complete his decompression.
On a large wreck without strong current, he could elect to fasten his reel line to the wreckage and ascend to his decompression depth. This would still keep him in a fixed vicinity and his bubble stream would identify his position for the surface observers. However, in a strong current an “up-line” can be impractical and it will be necessary to deploy a lift bag on the reel line to mark his position and then complete his decompression schedule while free-drifting beneath it. This is a less desirable scenario since the diver will move away from the wreck with the current, but an alert surface crew will be on the look-out for the lift bag and send a chase boat or recover the diver after the other team members are aboard. Most divers carry the lift bag in a BC pocket or attach it with shock cord to the cylinder where it’s out of the way until needed. To ensure it will be spotted, a high visibility color or painted reflective markings along with the diver’s name are added.
Okay, you’ve survived entanglement, silt-out, and gear failure while you made it to your stage tanks. And, in spite of being blown away in the current, you’ve deployed your lift bag and completed your decompression. Now you surface expecting the boat to be waiting for you. But Mother Nature has teamed up with “Murphy” to yank your chain a little more: fog or dense rain limits visibility to a wispy thirty feet or so. Aren’t you glad you brought that sonic alarm and a high intensity signaling strobe? In areas where fog can materialize quickly like the northeast, I recommend a collapsible radar reflector that can be held up on a “safety sausage” to aid the boat in finding you.
The investment in a few peripherals such as a reel, line, lift bag, signal device etc. are probably less than your bar bill on New Year’s Eve. These devices combined with a healthy dose of common sense and some defensive diving skills, will enable you to cope with most contingencies. It’s rare that everything goes wrong at once… but it’s nice to be prepared and have the confidence to implement safety plans quickly and efficiently. Training, experience, and an anticipation for the unexpected mark the diver who will manage effectively when a stressful situation presents.
Never expect things to go right and you’ll rarely be disappointed.