Diving Computers

  • Ocean Leisure after Brexit is Complete

    Poacher turned gamekeeper, after a career in the advertising industry I made a name for myself as the scourge of poor quality under-performing diving equipment, by exposing it in the UK’s Diver Magazine. It was a time when some manufacturers threatened to sue me and others invited me to visit their factories to discuss where they might be going wrong. It was almost a thankless task – one British importer has never forgotten that he was left with a garage full of unsalable regulators after I had revealed how badly they performed, conveniently forgetting I might have saved him from a manslaughter charge!

    Another went out of business, citing me as the reason the poor quality regulators he imported stopped being made, while a third British importer sent an email (a copy of which I still preserve) telling his manufacturer that the regulator they made was faulty and that if I, John Bantin, got to hear of it, they’d be ruined!

    Then there were the diving computers that gave you extra bottom time (at the expense of risk to your health). One doyen of American diving equipment manufacturers more recently told me I was a pillar of the diving community, conveniently forgetting the lawyer’s letters he’d sent me two decades ago.

    So what has this all got to do with Brexit? Well, all this went on before the days of EU regulation and the CE-marking of life-support equipment. I was testing regulators on an ANSTI machine long before it became mandatory for manufacturers to do the same and meet the EU-mandated performance requirements.

    Today, it’s difficult to buy life support equipment in the UK that does not meet these set standards. It does mean that it has taken the fun out of being a vociferous critic in print. Equipment reviews in diving magazines have been reduced to little more that rewritten manufacturer’s press-releases. However, I moved my talents to the US where I now write for an on-line subscription newsletter called www.undercurrent.org. The US makes rich pickings for someone of my talents and Undercurrent has no advertisers to try to please.

    The US has none of this regulation from which we have benefitted during the last 30 years in Europe. They have a system that waits for the problem to happen and then pursues the miscreants by litigation in the courts. Good news for American lawyers! Undercurrent is frequently full of reports of such cases. When Brexiteers boast that we will do away with European red tape and regulation, they mean following the American model. Bad news if you die, but don’t worry, your estate will be able to sue afterward!

    The Editor in Chief of www.undercurrent.org frequently asks me what equipment failures we have seen at Ocean Leisure. Started in 1975 as a direct counterbalance to the advertising-driven diving publications found in the US, exposing shoddy products is part of the life-blood of that publication. These examples of unsuitable or badly designed/manufactured equipment are frequently discovered on the other side of the Atlantic, but I surprise him by telling that Ocean Leisure in London rarely gets any life-support equipment for diving, or other water sports, returned because it does not meet manufacturer’s promise. That (some would say ‘evil’) EU regulation has seen to that.

    However, times might well change. Deregulation might be an opportunity for the importation of less good products into the UK and a return to the good old days for diving equipment journalists and their job of trashing the bad.

    What I can tell you is that the staff at Ocean Leisure are all keen users of what the store stocks. They are all either regular divers or sailors and will soon discover any suspect product so that you will not find them here. Leaving the EU might mean a future influx of poor quality imports but you can always rest assured that what you purchase at Ocean Leisure will be up to the task. You can use it with confidence.



  • Know What Your Computer Tells You!

    Depth and Ignorance Can Kill. Was it the lure of depth, his lack of awareness of how deep he was, or the inability to understand his computer? According to witnesses at a Cayman Coroner’s Court, Victor Crawford, a 62-year-old diver from Alabama and passenger aboard the Cayman Aggressor, had dived to a depth of 95 metres whilst using nitrox with a maximum operating depth of 33 metres. Health Services Authority pathologist Dr Shravan Jyoti said the cause of death was seawater drowning as a result of ‘nitrogen toxicity’.

    Mr Crawford went missing in March last year during a group dive before divers from Ocean Frontiers, a well-known Cayman technical diving operation, discovered his body. His death had been the subject of controversy when the ambulance took more than an hour to arrive at the East End dive shop to where he was recovered and then left without the body.

    Although witnesses said that the deceased was an experienced diver, Department of Environment deputy director Scott Slaybaugh said the case involved “a series of actions which were significantly hazardous and far beyond the standard of safe diving practices.”

    These included leaving the group to dive alone and ascending rapidly without making the decompression stops mandated by his computer.

    Coroner Eileen Nervik read statements of four witnesses to the case, before the jurors deliberated and came to their verdict of misadventure. (Abridged from the Cayman Compass)

    There’s a feeling of instant camaraderie among the passengers on a liveaboard dive boat because it’s in the interest of everyone on board that nobody has an accident. However, you don’t usually know everyone beforehand, neither do you know their levels of diving skill.

    A diving computer in time-keeping mode. A diving computer in time-keeping mode.

    We will never know what the true circumstances of this tragedy were, but it is likely the casualty did not read or was unable to understand what his computer was telling him. Clear calm water can be seductively dangerous.

    The water at Ras Mohammed, a wall  at the southern tip of Egypt’s Sinai, can be incredibly clear . The water here is said to be around 600 metres deep so you don’t want to drop anything. It’s so clear in fact that you can be misled into going deeper than you intended

    We might have all done that but imagine swimming alongside that steep wall of Shark Reef at 30 metres deep, breathing nitrox 32, and seeing one of your fellow divers in distant perspective way down below you?

    What to do?

    Already the dive had not been going as planned. Our dive guide opted to take the rest of the passengers in another direction and I found that as a former dive guide, I’d somehow been co-opted into leading this small group.

    We had intended to drop in at Shark Reef and swim round to Jolande Reef but the current was intense against us that we were all working hard at making any headway at all. Then suddenly I noticed this member of our group down at great depth.

    The water was so clear I could see that he was wearing a tank marked as containing nitrox just like mine so I took the risk of passing my maximum operating depth and hurtled down as fast as my ears would allow to signal to him to check his computer and follow me back up. He had been at almost twice the operating depth for the gas he was breathing.

    Imagine my horror when only a few minutes later he was back down at more than 50 metres deep, swimming along happily oblivious to the danger he was putting himself in.

    I swam down hurriedly again, thinking that it would be my bad luck if it was me that got an oxygen hit in the process of rescuing this diver who was totally unaware he needed rescuing. Again I signalled in an extremely animated way that he should look at his computer, pointing at his mask and then at my own computer that by now was singing a merry tune thanks to exceeding the maximum PO2 I had previously set on it. It was this moment at which he responded by offering me a naked wrist that indicated he was not wearing a dive computer.

    What an idiot. I was furious and took his arm firmly, dragging him back up to the apparent safety of 20 metres. I didn’t let go of him for the rest of his dive. Where was his buddy? It was his teenage son who’d obviously given up on his father and was swimming above us with two other divers, in the shallows, trying to conserve his air against the hard finning he was doing.

    I was angry to say the least. I kept thinking that this person whom was known to me only because we were on the same liveaboard boat, had forced me to take risks with my own health and seemed oblivious to that fact. On the other hand, had he gone missing it would have ruined the trip for everyone on board.

    Eventually, after a precautionary extra wait at 6 metres (since I had no idea of his dive actual profile and mandatory decompression stop requirements) we broke the surface at which point I emphasised in no uncertain way, “Nigel, if you forget to put on your computer, you must go back to the boat and get it.”

    If your computer was to display this, would you know what it meant? If your computer was to display this, would you know what it meant?

    His reply was unprecedented. He said in a quite matter-of-fact tone, “I decided not to bring my computer because it had stopped working. It went into SOS mode on the previous dive.”

    There are some fabulous new computers available at Ocean Leisure and the staff will be pleased to show them to you. However, they cannot demonstrate the core function of a computer without being underwater with you!

    Please read the instruction manual of your diving computer. Although you may always use it in No-stop diving mode, be aware what the display looks like should it go into Deco-stop mode. It will show a stop depth and either a total ascent time or a stop-time or both at this time. Don’t ignore it. Your computer will help keep you from danger, but only if you’ve read the instructions and fully understand its display.

  • An Intro to Diving Computers

    When we go under pressure, our bodies start to absorb the inert part of the air we breathe, the nitrogen. At normal atmospheric pressure we are saturated with nitrogen but by going underwater breathing compressed air, we allow our bodies to soak up more.

    Provided we stay no longer at depth than a slow ascent to the surface can give time for our bodies to off gas, we experience no problems. If we exceed these ‘no-stop’ times, we need to make stops at points during the ascent to allow our bodies to ‘catch up’ with this process.

    An advanced computer watch A typical computer watch

    All certified divers should know this and nowadays most wear a computer to monitor the potential state of decompression during and after each dive. I say ‘most’ because I have recently heard of cases of individual divers who eschew a computer saying ‘they know how deep and for how long they can stay’. This is very dangerous thinking.

    Of course, many years ago when computers were in their infancy, conservative divers refused to use them, believing a watch and depth-gauge combined with a decompression table was safer. They might have been safe if their watches and depth-gauges were accurate and they were disciplined in their use.

    One way to make leisure diving ‘safer’ in this regard is to breathe a gas with less nitrogen in the mix – nitrox – but it is only safer if you don’t take advantage of the longer no-stop times available. Stay longer and you still soak up just as much nitrogen as you would breathing air for the shorter no-stop time mandated.

    Computer manufacturers try to make things as safe as possible to keep them away from possible litigation. That’s why they build in a few precautions that sometimes casual users fail to comprehend.

    suuntodx_elastomerIf you dive with your computer set in ‘air’ mode, it will not allow you to switch to another mode such as ‘nitrox’ until a sufficient period has passed – usually twenty-four hours. If you want to switch between air and nitrox, it’s important to start off in nitrox mode, setting air as nitrox 21 (which it is).

    For the same reason, if you want to use your computer simply in ‘gauge’ mode, reading only depth and time, it will not be able to calculate your residual nitrogen levels should you wish to then switch to a nitrox or air diving mode, so it will lock you out for a period, up to forty-eight hours if you have been diving deep.

    Diving computers have a sampling rate typically of every 10, 20 or 40 seconds. Normally the 20-second setting is the default setting. During a leisurely dive this is entirely practical but it is not suitable for free-diving.

    Some computers have a mode specifically for free-diving when the sampling rate is much more often, even every second. This is because if you swim down to, say, 20-metres deep, a less frequent sampling rate might make a sample point at ten-metres on the way down and the next at 15-metres on the way up, totally missing the fact that you went to 20-metres in between. So gauge mode is unsuitable for use by free divers. You may need a computer with a ‘free-diving’ mode. Choose a computer that has the modes you require.

    Some of our customers tell us they want to free-dive between scuba dives. Current medical thinking believes this to add a degree of hazard to the activities because the scuba diver’s body will still be loaded with residual nitrogen at this time and that will be recompressed during a breath-hold dive. No computer can calculate for these short bounces while in diving mode because of the aforementioned sampling rates. For this reason, no computer should allow you to switch to free-diving mode while it is still calculating nitrogen levels during a surface interval.

    Some foolish divers will leave their computer to ‘off-gas’ at the surface while they go for a swim, ever tempted to duck-dive below the surface. That is a silly as leaving a computer tied off to a rope at the last decompression stop to ‘offgas’ while the diver climbs back on board. We positively do not recommend this. Nor do we suggest you buy a second instrument and switch between them during a day’s diving. That is the road to decompression illness.

    A diving computer can only monitor the nitrogen loading of your body if it is attached to you while you on-gas and off-gas. Use it properly and it will keep you safe – although, since everyone is physiologically different and the computer’s algorithm was written for a theoretically typical person, no computer manufacturer can guarantee this.

    Always read the instruction manual and be familiar with what you computer displays. Too often people go into decompression status during dives, especially where the water is warm and clear, and fail to understand that this is what their computer is telling them.

    A range of different computer displays at depth A range of different computer displays at depth
  • The Good, the Bad and the Ugly!

    Modern divers don’t know how lucky they are. An example of all the equipment sold in Ocean Leisure has been used and evaluated by someone on its staff and we are confident that it will all do what it promises. However, only twenty years ago there was a lot of diving equipment on the market that was not as good as it might have been. CE regulation and market forces have seen the products for diving mature and the bad old days are long gone but as a scuba diving journalist working for the leading diver’s magazine at that time, I took it upon myself to identify the good, the bad and the downright unattractive! I upset a lot of retailers at that time by promoting a regulator made in the UK by Apeks Marine Engineering. The company had little or no reputation for making good regulators at that time but it came up with a world-beater and I took pleasure in telling the world about it! I took a group of divers to 50-metres deep breathing off a single first-stage. The rest is history.

    Apeks regulator test Apeks world-beating regulator test back in the early '90s.
    Products were not always good. At the same time a manufacturer with a strong reputation came up with some new fins that were patently ineffective. I told the world. They were soon taken off the market.  There were plenty of other products that proved not to live up to their promise: A curved mask that gave distorted vision; a regulator that gave a wet breathe; a full-face mask that had some design defects that were quickly rectified by the manufacturer after I travelled over to Italy to dive with its boss and chief test diver. Then there was the computer that promised more bottom time. It was positively dangerous! The list goes on. There were even some BCDs that exhibited obvious defects once they were under water. You won't find any of those BCDs for sale at Ocean Leisure. Although there was plenty of good stuff too, the list of the less good seemed never ending back in those days and I didn't make myself a favourite with any of the manufacturers. I tried to make comparison tests as fair and objective as possible, for example taking computers on deco-stop dives attached side-by-side on the same rig. I even tested fins with teams of divers using underwater speedometers that I had especially made for the job.
    Underwater speedometer for comparing the performance of different diving fins. Underwater speedometer for comparing the performance of different diving fins.
    I'm pleased to report that all the diving fins offered for sale at Ocean Leisure did very well in the tests and most of those that did not have sunk without trace. So now when customers are confronted with a choice of similar products we can have the confidence to say that the right one is the one that suits you! The people at Ocean Leisure have masses of accumulated experience and they are happy to pass it on to you. Come in for a chat.

  • Nitrox - All You Needed To Know

    Know what you breathe before you take that plunge! Know what you breathe before you take that plunge!
    What is Nitrox? Air is mainly made up of two gases – 21% oxygen and 78% nitrogen (1% other gases). We metabolise some oxygen in the air we breathe but the greater part, the nitrogen, is inert. When we put ourselves under pressure, as we do when we go under water, our bodies absorb some of this inert nitrogen. As we go deeper and stay longer we absorb more. The time that we spend underwater is limited by the amount of that nitrogen we absorb. That is why we used to use tables or, more recently, a diving-computer. So why not breathe an air that has less inert nitrogen gas and so reduce the problem? If you’ve been breathing air, you’ve already been breathing nitrox – nitrox21. Other nitrox mixes have the percentage of oxygen increased and therefore the percentage of nitrogen is decreased. Nitrox 32 has 32% oxygen and nitrox36 has 36% oxygen.Nitrox Diving Breathing a richer nitrox mix instead of plain old air reduces the chance of decompression illness due to a diver staying down too long or coming up too quickly - providing no-stop times and ascent-rates for air are adhered to. If you want to continue with conventional levels of caution you can simply adjust your decompression requirement by adjusting your computer to match the nitrox mix you use and in that way get more time underwater.Scuba Jump However oxygen too has its problems too. Pure oxygen becomes poisonous at quite low pressures. It is currently thought unsafe to breathe pure oxygen at a greater pressure than 1.6 bars underwater and that occurs at only 6m deep. Therefore each specific nitrox mix has its own maximum operating depth and nitrox training agencies are unanimous in limiting the use of oxygen to 1.4bars of partial pressure within a mix with nitrogen._DSC0019 What you need to know is that the oxygen in air (nitrox21) can become hazardous at 54m deep. That does not affect leisure divers limited to an absolute maximum depth of 40m. A standard mix of nitrox32 should not be breathed deeper than 32m. Some training agencies tells new divers that this limit is 30m. Most popular sites for diving in the world now adhere to a 30m limit for leisure diving anyway. PADI Open Water Divers with Level One training are still limited to a maximum depth of 18m during training as before but suitably qualified divers can use nitrox32 to its full maximum operating depth (MOD).
    No additional equipment is need in the water. No additional equipment is need in the water.
    So for nitrox mixes up to 40% oxygen, no additional diving equipment is needed, only the knowledge of how to analyse the contents of a tank before diving, using the analyser supplied by the dive-centre and knowing how to set your computer to match. The day is foreseen when all new divers will start off breathing nitrox and air for diving will only be for specialised uses. More advanced divers that have been deeper than normal leisure diving depths use nitrox to speed up their decompression.
    Using a richer Nitrox in an additional tank to speed up decompression after a deep dive. Using a richer Nitrox in an additional tank to speed up decompression after a deep dive.
    They take additional tanks of rich nitrox with them and swap to these once they have ascended shallow enough for it to be safe do so. There are more advanced diving computers that allow you to set different levels of nitrox and to switch to the one that matches the actual mix the diver is currently breathing, and in that way track both decompression requirements and oxygen exposure accurately. All the diving computers sold at Ocean Leisure are nitrox compatible. If you want to know how to take high-speed sequences of pictures or successfully take photographs underwater, ask the guys at Ocean Leisure Cameras.

  • What a Fuss it Caused at the Time!

    Sometimes there’s a conspiracy of silence and you’d often do better not to disturb it. That’s what I inherited back in the day when I first joined Diver Magazine but I spoke up when others preferred to stay silent. My introduction to the readers was a gradual one with frequent if irregular contributions to the editorial content but by 1993 I had become a regular. The publication was a gentlemanly affair in those days. With no real rival to speak of, the publisher had a free hand to do what he liked but in fact became emotionally indebted to the the British Sub-Aqua Club that had given him a contract that was almost a license to print money in those days. His Technical Editor was among the BS-AC committee that had awarded him the contract so what that man said held sway. It didn’t seem to matter that he was also drawing a salary from a well-known manufacturer whose products also became de-rigeur in diving clubs. However, he was getting old and curmudgeonly and soon I in mere middle-age was able to replace him. I came from the world of the media and saw the monopoly afforded to the magazine as an advantage in that it could afford to offend advertisers if need be, if it was to the advantage of its readers. I believed that building the readership beyond club membership was the secret to a successful future for the magazine. For example, when the magazine proprietor asked me to explain to him what PADI was, he was obviously shocked. He hadn’t heard of PADI but even back in those days it was certifying more new divers with British addresses than the club was enrolling new members. Once the proprietor came to understand that there was a future beyond the comfortable confines of the club circulation he decided to give me a free hand to write features that might have been a little more controversial and informative than in the years before. I relished the idea. I started comparing regulators side-by-side underwater. This alone caused a furore. There were some shocks among the results. In those far off days before CE-certification, some regulators were clearly not good enough for anything more than the shallowest dive. Lawyer’s letters began to arrive but we weathered the storm. The proprietor told me to carry on. Advertisers withdrew their advertising revenue but with nowhere else to go in those days, they were soon back. Next I did an in-water side-by-side comparison test of seven popular dive computers. I went to Sharm el Sheikh where there was deep water directly off the shore and enlisted the help of Sarah Woodford, who was working as the local rep for Regal Diving at the time. Sarah still lives in Sharm. The plan was to take the computers, strapped side-by-side together on a rig, down to 50m deep, put them into decompression-stop mode and see how they differed in the information they dispensed during the ascent.

    The starting spread from the feature in Diver Magazine. The starting spread from the feature in Diver Magazine.
    It’s impossible to remember fast changing displays so key to the operation was the facility to take pictures of the displays at crucial moments whilst under water. Alas, during the initial moments of the descent, it was discovered that the camera had gone faulty. We retreated back to the beach and Sarah went off to find an alternative camera. It was more than three hours later that we able to get back in the water and by this time all the computers had recovered from their brief dip in the sea and their displays were clear. In those days computer algorithms varied widely. That's the mathematical calculation it uses to calculate nitrogen uptake. Nobody seemed to know what was correct. During our test dive one particular computer gave hours of no-stop time when compared with the others before flipping almost instantly into a very long deco requirement indeed. The whole exercise, including the aborted initial dip, was reported accurately in the magazine. My whole modus operandi was to tell the unvarnished truth to readers despite regular howls of protest in those days from manufacturers. The article was entitled "Learning Curve" and it caused yet another furore from both some readers and that one manufacturer. Firstly, I received an ocean of criticism from readers who said that I had broken a cardinal rule and should not have done a deeper dive second. It was if they were saying that when I discovered the camera wasn’t working, I should have gone down beyond 50m deep so that my second dive to 50m was shallower. I preferred to turn back before I’d loaded much nitrogen. History and current medical thinking bears me out that I was right but that was not what it said in the BS-AC manual at the time. More seriously, the manufacturer of the computer that was so far out of step with the others that it was almost laughable decided to threaten to sue me. Things were getting serious. It was only when it occurred to them that the other manufacturers would be enthusiastic witnesses in court on my behalf (they were hardly going to admit that their own algorithms were not safe) that it backed off. So it seemed I had upset both some readers and some advertisers. They would have all hung, drawn and quartered me if they could. I’m pleased to say that the failure to sell as many units as it would have liked eventually encouraged that particular manufacturer to offer an entirely different algorithm with its computers and today (twenty years later) all the different computers available in dive stores  are much more in agreement with what will keep the user safe – although none can guarantee it since everyone's physiology is different.  Provided you keep track of your dive profiles with a suitable diving computer it is no longer seen as essential to do the deepest dive first. If you've enjoyed reading this blog, you will enjoy Amazing Diving Stories by the same author.

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