I have been diving for a very long time indeed. Many years ago, before the term ‘Technical Diving’ was invented, I made a friend of cave diver Rob Palmer and we went diving together. He had some ideas on how diving could be made more adventurous without making it any more hazardous. We used ideas first put forward by Dick Rutkowski of NOAA. This included mixing extra oxygen with our air and even adding helium to it when we thought it gave us an advantage. Of course at that time we had to keep what might have been considered witchcraft strictly secret. The training agencies of the day would have pilloried us. Today those mixtures are called 'Nitrox' and 'Trimix'. We often took a pair of cylinders with us (a twin-set) filled with air but side-slung an extra tank that was as much as fifty percent oxygen so that we could cut short the otherwise onerous decompression-stop times that we needed thanks to the extra depth we went to. Sometimes, toting a massive camera, I preferred to avoid the extra encumbrance of the sling tank and made do with one cylinder of air alongside one of what we know today as a Nitrox mix of, say, thirty-six percent oxygen, both on my back. Rob introduced me to a giant of the diving world, Bret Gilliam. An American, Bret had worked for years as a US Navy diver, photographing nuclear submarines at depth when the only gas available was air. He held a record for the deepest dive on air at 150-metres deep and was and to this day remains one of the most competent divers I have ever known. Rob died later in an unfortunate diving accident (not related to the subject of this story) but Bret and I are close friends to this day, even if he does insist on calling me Mick Fleetwood!Bret was a technical diving pioneer with IANTD and then broke away from it to start TDI with Rob Palmer. Together, they wrote the first books on technical diving. If I am away in a comfortable diving destination such as Bikini Atoll or Truk Lagoon and want to dive a wreck that is just a little deeper than is suitable to use nitrox32 for, I still tend to dive with air and take a second cylinder with a richer Nitrox mix so that, in conjunction with a Nitrox gas-switching computer, I can reduce the mandated decompression-stop time I might otherwise need to endure if I only used air. This is where one gentleman in particular and a few other divers come into the story. My application of a simple rig of two independent cylinders on my back, swapping regulators when I got shallow enough not to exceed the maximum operating depth of the Nitrox, upsets some people because it was never written up in a textbook. Rob Palmer might well have done that had he lived and Bret has no problem with me using it. (I hasten to add it would be foolhardy to do this with a manifolded twin-set.) In some circles it has become known as ‘the Bantin rig’ and not always with polite intentions. My critics questioned what I would do if my air regulator stopped working (an unlikely occurrence) beyond the MOD of the Nitrox in the other tank, to which I answer that I would put the Nitrox regulator in my mouth and breath off that, making my way at a safe ascent rate up to where there would be no danger of oxygen toxicity. Oxygen toxicity is subject to total exposure that is both a combination of time and percentage. I have needed to rescue divers from more than fifty-metres deep more often than I would like whilst equipped only with a single tank of nitrox32 and although I wouldn’t ever recommend it, I am here to tell the tale. My critics seem to think it is OK to take a tank of Nitrox side-slung but not conveniently on my back. I hasten to point out that I am often doing these dives alongside those equipped only with a single tank. They wonder if I might put the ‘wrong’ regulator in my mouth by mistake. Well, anyone who does that probably should not be underwater in the first place. I go in with one regulator in my mouth and the other one is for the ascent. There is no confusion. A number of my friends including my wife have dived this way when it’s a dive that is suitable for this approach. The wreck of the San Francisco Maru in Truk and the wrecks in Bikini Atoll are good examples. It’s a way of having plenty of gas for what otherwise might be a deeper than usual dive and at the same time cutting long waits on the decompression bar. That one particular gentleman decided to become my bête noire on the Internet during the time I wrote regularly for Diver Magazine. It is ironic that he actually worked for Ocean Leisure in those days. Although I’m very happy to take four or more tanks with me if the dive requires it, as Bret Gilliam says, “If it works for you, that’s what matters.” Choose an appropriate solution and dive safely within your abilities..
Contrary to expectations of a sport that was years ago considered dangerous, there are few fatalities through scuba diving, but I was present in the Bahamas when a diver tragically lost his life during a dive. What happened? He went off on his own, ran out of air and at only around 18m deep he struck out for the surface. As designed, the Suunto computer he was wearing did not record the time he spent between 2m and the surface but it recorded everything else in its log and told the story. He probably made it to the surface but he dropped back down and drowned. He was a recently certified diver who had made a previous dive-specific trip so he was not totally inexperienced but why did he drop? When we recovered his body all his equipment was still in place. That is to say he was still wearing his weightbelt. Running out of air to breathe is obviously very serious. Every diver should manage their air supplies properly by keeping an eye on their pressure gauge. I admit that there may have been times when, distracted by an underwater photography subject, I have cut it very fine and arrived at the surface without enough pressure in my tank to inflate my BC. It’s not something I recommend but I’ve been able to orally inflate it instead. That’s what the oral inflation valve at the end of the corrugated hose is for. If this unfortunate person had reached the surface he could have done that but I am inclined to think that by this point he’d got into a panic and might have lost all sense of reason. He might have tried to use the BC’s direct-feed control but of course it would not have worked if his tank were empty.There is another option. Think about dropping your weightbelt in an emergency. Struggling to swim with full kit at the surface, if that diver had thought to drop his weightbelt he would still be alive today.You should not have to do this in order to swim up to the surface if you are correctly weighted to be neutrally buoyant, but you might need to do it once you are there. Dropping your weightbelt has the effect of making you buoyant so you don’t really want to do it at depth and enjoy an out-of-control ascent. You must also be careful not to drop it on divers that may be below you and for this reason practicing this act is discouraged at crowded inland dive sites. Before BCs, and their forerunner the ABLJ, were invented, dropping the weightbelt was enshrined in diver training. It was the only way to stay at the surface during an emergency. Correct use of a BC allows for neutral buoyancy at any depth and one only has to swim up a little for the gas within the BC to expand and start to become positively buoyant. You then need to jettison some air for reasons of controlling the speed of ascent. Dropping the weights effects a sudden increase in buoyancy that could get out of control. For this reason dropping weights tends to be glossed over in training. So how to drop a weightbelt? It used to be the last thing you put on in the old days. That was so that it was never fouled by other straps passing over it. Today, it’s often put on before the BC and tank.
It is not sufficient to simply flip the buckle and let it fall. You need to be sure it falls away cleaning from you without snagging. Think about dropping you weightbelt and its ramifications. Avoid being over-weighted so that you can be neutrally buoyant at any depth but know that you can always drop your weightbelt once you are near to the surface. Unhitch it and swing it away from you and once it is clear, before you drop it!