Monthly Archives: December 2014

  • How Long Will Your Air Last?

    The big question that every new diver wants answered is about how long the air in the tank will last. It all depends on how much there is to begin with, how deep it is going to be breathed at, and how much the diver is going to breathe it.

    How long your air will last depends on several factors including your own physiology. How long your air will last depends on several factors including your own physiology.
    The first two parts to this are easily identified. You can read on the shoulder of the tank its fixed volume and you can read from the pressure gauge how much it has been filled. Multiply one by the other. A 10-litre tank filled to 200 bar has 2000 litres of air in it. A 15-litre cylinder filled to 230 bar has 3450 litres of air. It is best to set aside a reserve of air and conventional thinking suggests that quarter of the initial supply is kept aside. This may be over cautious with a large tank but you have to make a judgement based on the circumstances you expect to encounter. Let’s assume that our 10-litre tank has only 1500 litres of air at our disposal with the rest (50 bar) is held in reserve. The next thing to identify is the depth the air is going to be breathed at. At 30m deep, the regulator delivers air at four times the pressure as it would at the surface. Thus if we are diving at this depth, we have only 375 litres of air compressed to four bar to breathe. The final part of the equation has a big question mark hanging over it. How much air do you need? A woman with small lungs will probably breathe a lot less than a male heavy-weight boxer. A man with large lungs will have the ability to pump a huge amount of air through his lungs. A relaxed man might breathe only eight litre every minute but increase his heart-rate by increasing his work load or stress him in some way, and this can easily leap to 30 litres each minute. It has not too much to do with fitness either. An old diver who has smoked all his life may not be very fit at all but if he is relaxed, and often that comes with experience, he will use less gas than a young trained athlete who is working harder than he should underwater. Even thinking hard uses a lot of energy. If you have to swim hard you will consume more than if you are merely hovering in the water. So what figure should we use for a breathing-rate in this calculation? Training agency manuals usually use a figure of 25 litres per minute in their examples of how to calculate air consumption. At 30m, our 10-litre tank (with 50 bar held in reserve) would last only 15 minutes. So what does it feel like to breathe from a regulator underwater? You can easily try this for yourself because it feels exactly the same as it does if you try it on land in a dive shop. You suck, there is a faint resistance and the valve pulls open. The mouthpiece floods with air that you inhale. It stops when you stop. When you exhale, there is also a slight resistance as the exhaust valve opens and allows that air to escape. It bubbles away past your head. Remember, the amount of air in your tank is divided by your respiratory mean volume or breathing-rate multiplied by the absolute pressure in bars at the depth at which it is breathed. If you can get your head around that you are well on your way to understanding your air consumption.

  • Choosing the Right Pair of Fins

    There is no doubt that a good pair of fins will enhance diving performance. The problem is deciding which are the most suitable fins for you. Assuming that you select a pair that fit you comfortably, fins can be conveniently divided into three types. The super-long fins beloved of free divers will propel the user a long way down below the surface with only a couple of kicks but would be very inconvenient to use for leisure snorkelling or for normal scuba diving. They’d just get in the way. Snorkellers want fins that are lightweight to carry and can be used in combination with bare feet or neoprene swimming socks. Many have a slipper integrated with the fin. There are also some open-heel fins with straps that can be used in this way. When it comes to scuba diving, most divers want to use fins in conjunction with neoprene boots. Ocean Leisure stocks nine or ten different types of these scuba diving fins in a price range from £50 to £187 per pair. So what’s the difference? They all work but some work better than others. If you were to try them all in the placid waters of a swimming pool, you’d be hard pressed to tell the difference in their performance. However, if you are going somewhere subject to strong current such as the Dampier Strait in Raja Ampat or any of the islands of Indonesia where the tidal flow forces through between the Indian Ocean and the smaller seas to the north for example, there will be moments when you need to get you head down and go for it. It’s at such moments as this that you will find if the performance of fins you’ve got is wanting or not. There has been some confusion also about the efficacy of split-fins. This design was originally conceived by American Pete McCarthy and sold under license to various manufacturers. The first company to buy into the idea was Apollo in Japan. They made their fins from a heavy rubber compound and they were very effective but were never properly imported into the UK and they weighed a tonne. Other manufacturers bought into the idea but concentrated on making their fins as comfortable in the water as could be possible at the price of loss of propulsion. They were seductive until you really need to propel yourself forwards. This had the effect of destroying the split-fin concept and today you may still hear people insisting that split-fins are no good. This is simply not true. There are some very good split-fins and some that are not worth bag space. The Atomic split-fin is one of the most effective fins available and I have proved that with the side-by-side comparison tests of fins I made over the years for Diver Magazine. I used a specially built underwater speedometer to objectively compare different fin performances and whereas some split-fins were very disappointing, the Atomic fins were not. Atomic also makes a less expensive paddle-style fin, if you don’t believe me! AquaBionic2 Another fin that will be up to performing well when the chips are down is the Aquabionic Warp 1. The designers went back to the drawing board for this one and came up with a fin that actually alters its shape according to the load put on it. Like the Atomic split-fin it’s not cheap but it makes the most of any effort you put in. I was in Raja Ampat at a site called Mike’s Point with two young fit Germans. We turned a corner in the reef where we had the full force of the flow presented to us head-on. The two Germans never made it any further whereas I was able to get past this current-point and make it to a lee in the reef further on. Later, they said that they were impressed at the strength of my kicking but this old-age pensioner knew it was because the fins I was using made the most of my muscle power. AquaBionic If you are off to any place with high-voltage diving, whether it be the Galapagos, Cocos, Aldabra, the Maldives or any of the archipelagos further East, I really recommend you invest in a pair of fins that won’t let you down. The pain of the price is soon forgotten and all you are left with is how good they are.  

  • Be Ready To Drop It!

    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.

    Make sure you get your weightbelt clear of your body before you drop it. Make sure you get your weightbelt clear of your body before you drop it.
    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!

  • Making Movies That Don't Bore Your Neighbours

    Movies4187Back in the day when I made television commercials, my first movie was quite an undertaking. It was 1980. I used a huge Panavision 70 camera, involved a lot of people with specialist skills, it cost £250,000 and lasted only thirty seconds, yet a lot of people bought a certain brand of tea because of it. A decade later, video cameras made things more economic. I shot the first commercially available instructional video for scuba diving. It only cost £10,000 to post-produce. Things have moved on apace since then and costs have plummeted. Now everyone can afford to shoot video. Some of you will only use your cameras for video clips, the moving equivalent of a snapshot. Indeed, often these clips get no further than being viewed on the LCD of the camera, never to be seen again. Others want to produce something more ambitious, in the form of a viewable programme. Whether you shoot on a Red Epic camera, digital DSLR, a compact or a little POV mini action camera like a GoPro Hero 4, air-side or underwater, the rules of move-making are the same. Still pictures can stand-alone whereas movies rely on the shot shown before and the one after. It’s a sequence that forms an event that might not have actually happened but it’s got to be believable to work. So gather your shots to tell a story. Look for an opening shot that will grab your viewer’s attention, something dramatic and something that can be used to bring your sequence to an end. Stories have a beginning, a middle and an end. Think of each short shot as a brick that will go with others to form the architecture of your final result. Bear in mind that your viewers may not be as engaged with your subject matter as you are and consider twenty minutes as the longest time they’ll watch your completed production before they make their excuses and leave. Continuity is crucial. Underwater, we have to think in terms of continuity of lighting, mainly dictated by the time of day and if we feature divers in a sequence shot over more than one dive, they need to be wearing the same kit in exactly the same way. Inserting a shot from night into a broad daylight sequence will never look right. Gather the shots that will become useful when it comes to constructing your movie. Shoot a wide establishing shot, a middle-distance action shot and close-up of each subject. You’ll be amazed how useful the material so gained with be when it comes to assembling a production. The subject moves and the camera remains still. Often more easily said than done underwater, but professional film-makers go to extraordinary lengths to keep their cameras steady while the action goes on in front of it. Ironically, the latest generation of little action cameras are harder to keep steady whilst recording. Following an animal as it moves is seductive when you are actually there but don’t do it for too long. It gets boring to watch. Let the animal move into frame, follow it for a bit and then let it clear the frame. These will give you the moments to cut from a previous shot and cut to the next one. A cardinal rule on land it to imagine there is a line down the middle of the path your moving subject takes. Never cross that line with your camera or it will look as if your subject has changed direction and gone back the other way. Less crucial with underwater subjects, ‘crossing the line’ often gives the impression that there is more than one subject, and that can make the action busy. “Not another video of blue fish!” I can still hear the groans of my friends from my early days of underwater video-making now. Light underwater is filtered so that only the shorter blue wavelengths penetrate much more than a few metres from the surface so if you are shooting elsewhere than the shallows, when a colour-correction filter over the lens will work, you’ll need some independent lighting to give you a full spectrum of colour. Increasing the camera frame rate from the viewed 25 frames per second to, say, double the speed, gives a slow motion effect. This smoothes down the action and is especially useful with fast moving underwater subjects and avoids that juddery effect often encountered when panning the camera at a normal frame rate. Slow-motion is almost standard procedure with professional underwater wildlife films. A cut-away is a shot that allows the editor to cut away from the main action for a moment and comes in very useful when constructing awkward sequences. The effect is to imply that these animals so recorded are bystanders to the main action. Luckily, you can use almost any underwater subject as a cut-away but it’s important that the camera is steady if these shots are to be inserted in a moving camera sequence. Once you get to edit your material, be ruthless. The cutting room floor is as important as the retained material. Choose the essence of the action. Keep it brief. Keep your audience wanting more not less. When you’ve got a lot of footage, the cameraman can be too emotionally attached and that is why Hollywood movies are traditionally edited by people who were not present at the shooting stage.Hammerhead and Video On the other hand, you might be just as happy collecting video clips that are the moving equivalent of snapshots. The choice is yours.

  • Getting a New Mask

    A New Scuba MaskIt’s always nice to get something new. My favourite old mask had seen better days. Its silicone skirt had yellowed and stiffened with time and probably too much exposure to tropical sunlight so I got hold of a new one. The staff at Ocean Leisure avoid recommending any particular mask from the huge range they carry because a mask is such a personal item. Instead, they encourage you to come in to the store and try them all so that you go away with one that sucks on to your face nicely and thereby does not leak. I’m very lucky in that I seem to have a face that gets along with almost any mask despite my ill-groomed facial hair and the latest TUSA mask was said to have a super-flexible silicone skirt so fit was never a worry. They say that there are two types of people past middle-aged: Those who wear glasses and those who never read books. What was a worry was the fact that in common with many people over the age of forty-five (I’m well over that) my eyesight is no longer as good as it was. Similarly, many people suffer short-sightedness from birth and wearing a mask in conjunction with contact lenses can inhibit the freedom to take it off underwater. I still remember the time it took me to feel carefully along the bottom of a swimming pool in a desperate search after one of my trainees lost a contact lens during a mask removal exercise. Naturally, I found it. A good instructor as ever, I wasn’t ever going to let anything spoil my trainee’s day. When it comes to choosing a mask, if you are so afflicted by imperfect vision, you’ll want a mask that will take prescription lenses and that reduces the choice available. However, it’s a much better option than battling with contact lenses underwater. Now, I might add that you may not need lenses that completely match your prescription since even the clearest seawater is quite poor optically but an approximation with do and go a long way to getting you the maximum enjoyment from getting your head underwater. If you want to be good at something, you’ve got to practise. I took home my shiny new mask and a set of lenses with the intention of installing them. I’ve worked in the diving industry for a generation and yet I found difficulty in taking the mask apart. Even a phone call to the distributor who sent me a special tool for the job left me pondering how to get the old glasses safely out. It’s simply that every mask seems to be different and I’d only done this about once every five years. If I had been clever, I should have let one of the helpful staff at Ocean Leisure do it for me. They do it virtually every day. Well, I managed to successfully install the new lenses at the end. I then merely had to get rid of the inevitable and invisible silicone deposit that gets on to the inner side of the mask glass during manufacture. The safest way too do that it to rub a bead of old-fashioned white toothpaste around the surface to gently abrade the silicone deposit off. Otherwise, it gives an edge for tiny droplets of moisture to cling to, precipitated out of the damp air inside the mask while you are using it with the dreaded fogging effect. After that, each time before you go under water, simply spit on the inner side of the mask glass and rub the saliva around before giving it a rinse in seawater. If you don’t fancy doing that, there are proprietary products available that do the same job.TUSA When it comes to choosing a skirt, the choice is usually between clear silicone or opaque silicone. Some divers swear that a mask with a black skirt gives them better vision. I suggest that a transparent skirt gives you a better feeling for what’s around you. Just like driving a car and looking through the windshield, the side windows of the car don’t destroy your forward vision but certainly make the car less claustrophobic. That said, some like to look like Zorro or Batman with a black-skirted mask and who am I to argue with that? It’s a question of personal preference. My best advice is to get one that fits you well with lenses that suit your eyesight. Almost without exception, the people at Ocean Leisure can either fit factory-supplied lenses or lenses with specific prescription to any mask you choose from the wide range available in-store. Mask1734

  • Who Am I and Where Did I Come From?

    Bantin's BlogI used to be technical editor of Diver Magazine, but after twenty-one years as an active diving journalist, travelling all round the world and experiencing a wide range of conditions I decided to retire. I’d been going on dive trips every month and sometimes more often than that. I calculated I had made more than two hundred and fifty of these expeditions and that’s a lot of dives! After doing multiple plane journeys for dive trips to many different distant exotic sounding places, I was starting to feel jaded. Yes, you can have too much of a good thing – eventually! However the inactive life of retirement didn’t sit well with me and a year later I decided I still wanted to make use of the huge amount of knowledge I’d accrued about all manner of diving locations, technique and underwater photography and found an outlet for this at Ocean Leisure, probably the most comprehensively stocked dive store in London. Within the first week I was meeting some customers, old friends, that I had last shared a cabin with in places as far away and as far apart as Papua New Guinea and Costa Rica’s Cocos Island, as well as making a great many new friends too. What really impresses me about the people who work at Ocean Leisure and Ocean Leisure Cameras (a store within the store) is the vast amount of product knowledge that they have at their disposal. They are almost without exception young; many are multi-lingual and, of course very enthusiastic about their subject. In fact at first I felt a little bit out of my depth and that’s the first time in a very long time indeed. If you want to talk about diving, I’m your man, but I’m still learning about the incredibly comprehensive stock held at Ocean Leisure. This is especially true in the camera department because the advances in digital camera technology during the last couple of years are unprecedented. For example, that annoying lull between pressing the shutter release and recording a picture, experienced with older compacts, has more or less disappeared. Then there’s the ever-onward marching technology of GoPro. These tiny little cameras are suitable to taking places where you would never have dreamed of taking a camera before and they simply marched off the shelves as the must-have Christmas present for 2014. Ocean Leisure Cameras stocks a massive range of accessories that will allow you to combine a GoPro with your favourite all-action activity. When you visit, I’m easy to spot. I’m the older person. Please bear with me if I need to ask one of the young blades where to find something that you are particularly interested in. It’s an Aladdin’s cave of diving and underwater photography equipment!

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