Looking at the incident reports, one category of diving incidents that comes up time and again is lost contact with divers on the surface. Divers surface away from the boat and are not spotted. The boat breaks down and looses contact with divers. Shot lines drag under while divers are decompressing and the boat looses its visual reference. Delayed SMBs are missed in heavy seas.
These are just a few typical situations. On top of this sort of thing, just how many “diver lost, never seen again” situations actually included the diver reaching the surface?
Now I will make a digression. A little story I heard years ago about a branch of science called operational analysis, an analysis that looks at the whole problem mathematically.
In the Second World War patrol aircraft would search areas of sea for surfaced or snorkelling U-boats. Upon spotting a U-boat the aircraft would dive to attack it with depth bombs. Upon spotting the attacking aircraft the U-boat would crash-dive and make an evasive turn.
Due to the non-compressible nature of water depth bombs have a greatest effective blast radius at a particular depth, so that was the depth they were set to explode at. Seems fairly sensible at a first glance, set the bombs to explode at the depth where they gave the biggest bang and you stood more chance of killing the U-boat.
The trouble was they were not killing many U-boats! A bunch of scientists were locked in a dark room and told to solve the problem. They looked at dive rates, speed and turn rates of U-boats, the relative effective radius of the depth bombs at various depths, the spread of the pattern dropped by attacking aircraft and no doubt many other factors that either I can't remember or were not in the story when I heard it.
The conclusion was that by the U-boats were often too shallow to be killed by the exploding depth bombs. Furthermore, if a U-boat actually reached the critical depth, it would also have time to turn far enough to evade the bombs. Either way the bombs were wasted.
The solution was to set the bombs to explode at shallower depths. They had a lower effective blast radius, but they were more likely to be close enough to the U-boat to do some damage. The kill rate improved significantly.
So what has this got to do with diving? To my knowledge no one has ever made such a first principle analysis of diving safety. The safety equipment required by training agencies and the actual safety skills taught to divers have never been put through such an analysis.
The HSE regulations for diving at work now require a risk analysis for each diving project. This applies equally to commercial diving, dive schools, media and scientific diving. A positive step towards to a more rational approach to diving safety.
Unfortunately many diving operations are missing the point. They take a booklet such as BSAC's Safe Diving Practices or the equivalent PADI standards and turn it on its head by inventing a risk and an analysis to justify each safety measure. They end up with a nice thick report called a risk analysis that tells them that they should be following the original booklet, but does it really achieve anything other than satisfying red tape?
In general I would describe the sport diving approach to safety policy as “knee jerk analysis”. A reflex action to an immediate stimulus.
“If the diver runs out of air he could drown”.
“OK, make them all carry octopus regulators and dive in buddy pairs, that should solve the problem”.
To be truly valid we need to go back to first principles and make an analysis of diving safety from the ground up. For example, having an alternate air source is intuitively better than not having an alternative air source. I won't argue with that. But would more lives be saved if we spent the equivalent amount of money on surface location aids such as yellow flags, EPIRBs and strobe lights instead of octopus regulators and long hoses?
The truth is that with the current state of incident reporting and analysis we just don't know. Even if the will to question such basic assumptions of diving safety existed, there may not be the data available to conduct a thorough analysis. Incident reports only get filed when things go horribly wrong. There is little record of incidents avoided by appropriate use of safety aids and application of safety skills.
Just how often are divers forced to approach their buddy for an alternate air source? Then having made an ascent, the incident is forgotten and never enters the overall statistics. How many times have divers been “lost” for ten minutes, then re-located by their cover boat before things got too serious? And what location aids were they using?
Maybe this example is a bit extreme, but look at another item of supposedly “compulsory” diving equipment, the snorkel. An item that many experienced divers don't bother to carry. Even divers that do carry a snorkel often prefer to surface swim on their backs. Would more lives be saved if the money new divers spend on a snorkel to complete their basic equipment was spent on a yellow flag?
If money is no object, then every diver can be fully equipped with all kinds of safety devices. But most divers don't have infinitely deep pockets and don't want to cart around so many items of equipment. So we come back to my original point. Maybe it is time for a more critical approach to the analysis of diving safety. There could be some surprises in store for us.