DROPPING A
BOMBSHELL
Diving could well be safer, says John Liddiard, if we ditched our basic assumptions and learnt to think the unthinkable
In diving incident reports, one problem seems to come up time and again - lost contact with divers on the surface. Divers come up away from the boat and are not spotted. The boat breaks down and loses contact with divers. Shotlines drag under while divers are decompressing and the boat loses its visual reference. Delayed surface marker buoys are missed in heavy seas.
These are just a few typical scenarios, but how many "diver lost, never seen again" situations include the diver reaching the surface?
Now I will digress, to tell a little story I heard years ago, about a branch of science called "operational analysis", a system of solving problems mathematically.
During World War Two, patrol aircraft would search areas of sea for surfaced or snorkelling U-boats. On spotting one, the aircraft would dive to attack it with depth bombs. On spotting the aircraft, the U-boat would crash-dive and make an evasive turn.
Depth bombs have a greatest effective blast radius at a particular depth, and it was at this depth that they were being set to explode.
This seems sensible enough; set the bombs to explode at the depth at which they give the biggest bang, and you stand more chance of killing the U-boat.
The trouble was, the bombs were not killing many U-boats! A bunch of scientists were locked in a 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 bombs at various depths, the spread of the pattern dropped by attacking aircraft and so on.
Their conclusion? The U-boats were often too shallow to be killed by the exploding depth bombs, and if the subs reached the critical depth, they would have time to turn far enough to evade them. 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 were more likely to be close enough to the U-boat to do some damage. The kill rate improved significantly.
So how is this connected with diving? To my knowledge, no one has ever gone back to first principles in analysing diving safety. The safety equipment required by training agencies and the safety skills taught to divers have never undergone such a process.
The HSE regulations for diving at work now require a risk analysis for each diving project. This applies equally to commercial diving, schools, media and scientific diving, and is a positive step towards a more rational approach to safety.
Unfortunately, many diving operations are missing the point. They take booklets such as the BSAC's Safe Diving Practices, or equivalent PADI standards, and turn them on their heads by inventing a risk and an analysis to justify each safety measure.
They end up with a nice, thick report called a "risk analysis" which tells them they should be following the original booklet, but does it do anything beyond satisfying red tape?
I would describe the sport-diving approach to safety policy as "knee-jerk analysis" - a reflex action to an immediate stimulus: "If divers run out of air, they could drown."
"OK, make them all carry octopus regulators and dive in buddy pairs, that should solve the problem."
What we need to do is analyse diving safety from the ground up. For example, I wouldn't argue that having an alternative air source is intuitively better than not having one. But might not more lives be saved if we spent the equivalent cash on surface-location aids such as yellow flags, EPIRBs and strobe lights, instead of octopus regulators and long hoses?
With the current state of incident reporting and analysis, we simply don't know. Even if the will to question such basic assumptions existed, the data might not be available to conduct a thorough analysis. Incident reports get filed only when things go horribly wrong.
What record is there of incidents avoided by appropriate use of safety aids and application of safety skills? How often are divers forced to approach their buddies for an alternative air source? Having made an ascent, an incident is forgotten and never enters the overall statistics.
How often have divers been "lost" for 10 minutes, then re-located by their cover boat before things got too serious? And what location aids were they using?
If this example seems extreme, look at another item of supposedly "compulsory" diving equipment, the snorkel. Many experienced divers don't bother to carry one. Even those who do, 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 were spent on a yellow flag?
If money is no object, every diver can be fully equipped with all kinds of safety devices, but most don't have infinitely deep pockets and don't want to cart around so many items of equipment.
Perhaps it's time for a more critical approach to the analysis of diving safety. Who knows, there could be some surprises in store for us.
Appeared in DIVER - May 2000
