If Archimedes had been taking a shower instead of a bath then it might have been centuries before somebody else came along and defined the principles of buoyancy.
It was a random thought that popped into my head while I was standing under the shower. On this occasion, my thought processes received a boost when, looking up to see if the ceiling needed repainting, hot jets of water shot right up both nostrils and started a coughing and spluttering fit.
A bloke of Archimedes calibre would probably have made something more of this modest discovery. Nevertheless, it did start me thinking about the advantages of baths and how deep one would need to be before the water lapped up to the level of my nose? A train of thought that in turn led me to the conclusion that what seems to be lacking in diving is a clear definition of many of the terms in common usage.
Take the word, ‘deep’, for example. We all have a subjective view of what is meant by ‘deep’, but ask any group of divers for a precise definition of the word and the chances are that the answers will vary enormously. It is, after all, a relative term.
During the nineteenth century, anyone who worked underwater wearing a helmet, suit, lead boots and heavy weights was, to the layperson, a deep-sea diver – even if they were only in 3-metres of water. With the introduction of decompression tables it began to be assumed that deep diving only applied to depths greater than 10-metres, the point at which, in those days, decompression obligations were considered an issue.
The 10-metre demarcation line received a further boost following oxygen toxicity experiments on Royal Navy divers using O2 rebreathers during the first half of the last century. Assuming that the body could safely tolerate a partial pressure of oxygen up to 2 atmospheres absolute, those Royal Navy divers trained on oxygen rebreathers to a maximum depth of 10-metres were designated as ‘Shallow Water Divers’.
Air, of course, has its own problems; notably nitrogen narcosis, an often debilitating condition that – depending on individual tolerance – tends to become more noticeable at depths beyond 18-metres. In 1953, recognising the problems imposed by narcosis as well as the then existing limitations of carrying an adequate supply of gas, Cousteau suggested a depth restriction of 40-metres for divers using SCUBA; an arbitrary figure supported by the U.S. Navy’s recommendations on SCUBA diving operations.
These depth parameters have since been adopted by many of the recreational diver training organizations, with 18-metres once considered the starting point for ‘deep diver’ training and 40-metres – until recently – the generally recommended maximum depth limit for recreational diving.
Neither of which depth limits adequately defines, ‘deep’ diving. Try telling a Technical Diver that you’re a qualified ‘Deep Diver’ when the deepest you’ve ever been is 21-metres, and the chances are that your reputation as somebody who’s worth listening to will be sullied forever.
Not that knowledge or understanding of physics and physiology is a pre-requisite to performing dives beyond the 40-metre mark. Thanks to technology and the techniques pioneered by those who had a set purpose in diving to extreme depths, recreational/technical dives to 100-metres and beyond have become commonplace; particularly with the widespread adoption of trimix and Closed Circuit Rebreathers.
Even those individuals and organisations who once advocated the use of air as the breathing medium in deeper dives now recognise the benefits in adding a squirt or two of helium to the mix; especially when it assists in the establishment of a depth record.
Not everybody agrees with me, of course, but I’ve long held the view that trying to set a depth record on SCUBA for no other purpose than to have your name listed in the Guinness Book of Records, is not dissimilar to stuffing one or two half-starved ferrets down your trousers: the risks are great, and there’s a very real danger that critically important body parts may not survive the experience intact.
It’s not even a case of, “boldly going where no man has gone before.” – I’m referring to the depth thing, not to letting live ferrets loose in your underwear. Offshore commercial divers, for example, regularly spend hours working at greater depths than those ever achieved by SCUBA divers.
The upshot of all of this is that enormous numbers of recreational/technical divers and dive leaders have become very blasé about regularly diving to depths that were once regarded as deep: which is not to suggest that there’s no point in performing deep dives. After all, part of the adventure of diving is in executing a properly planned, mission-oriented dive of discovery. Rather, it’s to highlight the fact that until such time as we sprout gills there’s no such thing as a simple dive and that all dives, regardless of depth, deserve to be treated seriously and with the greatest respect.
And just to bring this back to buoyancy: when I’m neutrally buoyant and floating at eye level, the tip of my nose is about 7 centimetres below the surface of the waves; and when I’m standing upright on the seabed, my nostrils are about 164-centimetres above the soles of my feet. I figure that’s as good a reason as any for taking the cautious approach and regarding any depth of water greater than 1.64-metres as ‘deep diving’.