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Wildlife and Underwater Cameraman Mark Sharman Gets Certified on his POSEIDON SE7EN

Wildlife and Underwater Cameraman Mark Sharman Gets Certified on his POSEIDON SE7EN

By Mark Sharman

Mark_Rebreather_Profile2014 has started off in the best way possible, by spending two months diving and filming in the Red Sea. With new kit to test out and get my head around in my new Nauticam housing for my 5DmkIII and POSEIDON SE7EN rebreather unit, I faced a steep learning curve to get my head around those two set ups.  Thanks go out to all the sales advice and support I received from Simon Morris of Poseidon Diving Systems Ltd. Great to know he’s always there should I need extra bits and pieces.


Emperor Divers agreed to host me during a tour of all their diving locations in the Red Sea, in exchange for making and delivering a number of promotional films from each site. It was a good deal, and a brilliant way to practice with the new set up. I now have a lot of editing on my hands to deliver my part of the deal… Don’t worry, they are coming!


SPP_1381Before my time with Emperor Divers started, I first had a week on Blue O Two liveaboard Blue Fin, to carry out my PADI recreational rebreather course with instructor Adam Wood of Divemaster SCUBA. Also on the course were BBC NHU producer Ted Giffords and a lovely German lady called Veronika Kruse. And what a steep learning curve that week was!


It has been a big ambition of mine to become a rebreather diver, and after several years of waiting, the time was right to do it now, ahead of the 2014 filming season getting underway. Normally, my workload drops during the quiet winter months, so a perfect time to retrain, reconnect with some long-held ambitions and take another plunge into the deep end.


After a lot of research and thought, I opted to purchase the POSEIDON SE7EN unit ahead of the trip. For my purposes, and being a beginner with the technical side of diving and rebreathers, it seemed to be the best unit to start with and for my underwater camerawork too… Not needing to be constantly monitoring gauges, being allowed to spend more time focussing on the camerawork itself. However, it does come with the potential drawback in that because it is a recreational unit, it doesn’t give you the option of sorting out any problems which arise during a dive, which technical rebreather divers can potentially solve and carry on the dive. With the Poseidon, if the computer senses a problem, the only response is to bail out onto open circuit and abort the dive. Not ideal when in the middle of filming rare underwater behaviour! Only time will tell if this will cause me an issue with my work or not… the jury is out for now!



That aside, it was great to finally experience the main advantages of rebreather (closed circuit) diving: Hardly any bubbles whilst diving – your breathing gas is re-circulated, scrubbed of its CO2 content, injected with fresh O2 and re-cycled back into a breathable gas. It makes the world a silent one down there, and fish/other marine life is far more open to approaching you and getting on with their behaviour, as your normal open circuit bubbles are not there making a noise. It makes for a lot more relaxing and engaging dive with what’s down there. Plus breathing warm, moist air is so much more comfortable than dry, cold air with open-circuit.


_MG_1850The other big advantage, is that it creates long, almost limitless, bottom times. You pretty much can’t run out of breathing gas on a dive, despite only taking down two three litre cylinders with you (one air, one O2). Air consumption is not the limitation as it is with normal scuba diving, and it makes for the best advantage to a diving experience. A two or three hour dive is no problem whatsoever, particularly in the warm waters of the Red Sea, and a with P-valve in my dry suit fitted before the trip! Most noticeable was being able to dive for two hours on the Thistlegorm, one of the best wreck sites in the world, and probably my favourite dive site, when most scuba divers are lucky to manage a 45 minute dive on it. Also, being able to cover all four wrecks on the Abu Nu Has reef, that was a special dive and a highlight during our course. These advantages open up a whole world of new possibilities and it is very exciting.


I had heard that learning how to use a rebreather was like learning diving again from scratch: It is a completely different way of finding and maintaining neutral buoyancy, the all important essential skill required for good underwater camerawork, and forever the primary concern on a dive with a camera. And they were all right of course!


DSCF1236 (1)Unlike in SCUBA, whereby you use your breath control to maintain your neutral buoyancy and position in the water: breathe in and you ascend, breathe out and you descend. These rules do not apply to rebreather diving, because your volume of gas remains the same as you breathe in and out of the counter-lungs, so your body position doesn’t alter when breathing, which is a well-developed instinct from SCUBA required to forget and learn again from scratch. Instead, neutral buoyancy is found by adjusting the air volume in your dry suit or BCD/wing… So generally you opt to swim around obstacles rather than over them, ascents with rebreathers cause more hassle than you can imagine to an inexperienced user!


I discovered through using the rebreather a bad habit I have developed on SCUBA: breathing out through my nose, or letting a constant trickle of air out is something you can’t do when diving on a rebreather. Letting air out of your nose is the way to let out gas from the breathing loop, therefore reducing your volume and making you descend. So that has been the hardest habit to stop, and I am glad I can say I no longer breathe out of my nose unconsciously!


BannerFishClose (1)Despite the early difficulties of learning these new techniques, progress was quickly made and by the end of the course, a lot had fallen in place and it was no longer the alien feeling as it was on the first dive or two. Or so I thought! In reality, it has taken most of the two months I’d given to learning my unit (and working a camera simultaneously) for it to really click. My underwater camera peers recommend spending at least 100 hours on a rebreather for it to really click and be in a position to work on it. Of course they are right. I have found that after about 80 hours of diving, it has become natural and it makes sense and I’m ready to take my underwater camerawork to the next level on the back of these two months. I can’t wait to carry on diving with it back in the UK and getting my first work with it this year.


Mark Sharman will be a regular contributor for the Poseidon Blog, stay tuned for future editions!


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