He has reviewed open-circuit and closed-circuit training courses, but this time Chris Boardman was heading for the Red Sea in search of a halfway house. Would a semi-closed circuit rebreather turn out to be his dream machine?
THE TWO TURTLES ACCOMPANIED US FOR A GOOD 15 MINUTES in the strong current that whisked us along Jackson Reef. The female of the pair was a little reticent but kept pace with our group, hiding behind rocks as she went. The big male was considerably more confident, and not a little curious. Equipped with my super-stealthy rebreather, I watched from 5m away as the male repeatedly rubbed his mottled shell against Craig Nelson's camera. As Craig was using nothing more sophisticated than a standard 12 litre cylinder, I was beginning to wonder what the point of wearing this complicated machine was. The advantages of fully closed-circuit rebreather (CCR) diving were made clear to me on the TDI course I reviewed in Cornwall (Diver, September 2002). The Draeger Dolphin is a less complicated semi-closed offering than the AP Inspiration CCR and has been around for some years. But are the advantages worth all the hassle? I wanted to find out for myself, and to do so, it was back to Egypt, to Sharm el Sheikh and an outfit familiar to British divers, Red Sea Diving College. Its situation, only 50m from the gently sloping sandy beach in Na'ama Bay, makes it ideal for conducting diver training - and reviews of that training. Photographer Craig and I were staying with the Red Sea crowd to review three of PADI's popular 'specialties', one of which was its Semi-Closed Rebreather course. My fellow-student on this occasion was Red Sea's resident Russian instructor Surguei. A real character he turned out to be! If ever anyone fitted the stereotype of a Russian, it was Surguei. Only about 5ft 4in but with shoulders so broad he was virtually the same height lying down, he resembled the chef from the Daily Express Beau Peep cartoon strip. During the two days we were with him, he stopped smoking exactly twice - both times while he was under water. When I asked him why he was interested in getting to grips with the semi-closed-circuit rebreather, this sophisticated piece of diving equipment, he replied with a single word in his guttural accent: 'Bored.' Surguei was not a complicated bloke. Our instructor was Terry Johnson, an accomplished technical diver who has been diving for 18 years and teaching for the past six. He started in the UK before seeing the light and moving to Sharm, where he has lived with his family ever since. As the course went on, Tel would emerge as one of those annoying people who can keep mathematical formulae in his head and is unable to grasp why I can't!
day 1 We first had to get to grips with the theory behind these semi-closed units, so the better part of our first day saw us installed in the small, air-conditioned bar adjoining the dive centre. First, we ran over the main differences between SCCR and open-circuit scuba, along with the perceived benefits. According to PADI's instructor manual, these include: fewer and smaller bubbles allowing you to get closer to aquatic life; quieter operation; gas use independent of depth; and dive duration that would normally require two or three cylinders in a smaller package. Further advantages included the gas breathed being warm and moist, because of the chemical reaction of the scrubber material, and the fact that, should a problem arise, SCCR generally allows the diver a little more time to react. We moved onto an explanation of how the DrÃ?ger unit achieves this. Gas is fed to the diver via a 'controlled leak'; your breathing action circulates this around a loop, passing through a carbon dioxide absorbent on its way back to you. After re-breathing the now-cleaned gas about four times, the excess is vented into the water via a small overpressure valve in the back of the unit. Because the gas is not supplied on demand, but at a constant rate, one can calculate how long the supply cylinder will last before the dive starts. Depth has no effect on the amount used. Although many of the principles are the same, the DrÃ?ger Dolphin is much simpler than a fully closed-circuit unit, and requires no electronics. Unfortunately, the system has the disadvantage of having to use a single nitrox mix, whereas a CCR 'blends as you breathe'. You are therefore limited to the maximum operating depth (MOD) of the mix in the supply cylinder. Duration can be as much as two hours from a 4 litre cylinder, but otherwise decompression obligations are no different to those that arise when using nitrox with open-circuit equipment. As this was the case, most of the classroom work was more like doing a nitrox course than anything else, involving the use of lots of tedious little equations. For the next two hours, Terry worked through the instructor manual, asking us questions as he went. It became clear that Surguei was struggling with the combination of English and the London accent Terry was throwing at him. His eyes kept darting towards me as a possible bail-out. Unfortunately, my outstanding mathematical abilities meant that I was largely unable to oblige. After we became comfortable with the necessary maths and able to work out our adjusted no-decompression limits, MODs and maximum dive time, we moved outside into the scorching heat of the centre courtyard to put the units together. This turned out to be a fiddly affair, requiring the connecting of hoses to breathing bags; filling the scrubber canisters and trying to get it all to fit together like a 3D jigsaw. With pre-dive checks, this took about 40 minutes. It was made slower by the fact that Draeger has managed to make every single fitting unique to this unit. Not even the cylinder valves used were standard. Finally kitted up, we strolled across the walkway onto the beach and down to the water. In the near 40Â? heat, it was a tremendous relief to get wet. Probably the most important part of using any form of rebreather are the checks made immediately before submersion. Most fatalities among SCCR and CCR users occur either at or near the surface because, unlike open-circuit, it is possible to breathe from the loop without turning on the gas supply. As the user breathes, the oxygen content will slowly drop until it becomes too low to support consciousness, which may result in drowning. The added danger with a DrÃ?ger unit is that oxygen monitors do not come as standard, meaning that there would be no indication of this oversight until the onset of symptoms. Terry suggested a simple acronym to help us remember the three simple steps for avoiding this: Gas, Gauge, Gag. Gas: Turn on the supply, something done at the last minute to conserve the nitrox. Gauge: Check the contents gauge to ensure that you have done this and have sufficient gas for the dive. Gag: Only after these two checks do you put the mouthpiece in. As we submerged, I remembered the quirky buoyancy characteristics of rebreathers; breathing has virtually no effect on buoyancy, and all adjustments have to be made manually with the BC. Once 'set' it is possible to lie motionless in the water, however, a very pleasant sensation. We spent the next hour swimming around the shallows doing a few simple drills such as mask-clearing (remembering that the counter lungs are emptied as you breathe the contents out through the nose) and replacing the gas in the now-empty loop. This is simple with the Dolphin, because when the counterlung is empty, sucking in opens a demand valve as with a normal regulator, refilling the loop with fresh nitrox. We also practised switching to the bailout regulator, and even swimming without a mask, remembering to breathe out through the mouth and not the nose. All of this was quite simple, the only small complication being the need to keep the mouthpiece closed whenever it leaves the mouth to prevent the loop flooding. Skills finished, it was time to ascend. Because of the overpressure relief valve on the back of the Dolphin, which vents off the excess in the breathing loop, ascents are similar to open-circuit, the only expanding gas that needs to be dumped being that in the BC. Back at base, it was time for unit-cleaning. What a palaver! As the warm, wet hoses and counterlungs provide a perfect environment for bacteria growth, after each day's diving the whole thing has to be stripped down and cleaned thoroughly. The worst part of this is the half litre of drool collected in the water trap. This is absolutely gross and the aspect of rebreather use I hate most. Last thing on the agenda for day one was the knowledge review. This we did verbally with Terry, back in the bar.
day 2 Theory complete, it was out on the boat today for a spot of wall-diving on Thomas and Jackson Reefs, an hour's sailing out of Na'ama Bay. On route, we analysed our supply cylinders, filled the scrubber canisters with fresh DiveSorb and assembled the units. With pre-dive equipment checks, this took a tedious 45 minutes. We then retired to the cabin for a further 30 minutes to work out our maximum depth, dive duration and no-decompression limits. Bottom depth for dive one was 30m, and as we levelled off, a large whitetip reef shark cruised below us. As the air supply is unaffected by depth, this is where a semi-closed unit comes into its own. As our open-circuit counterparts made their way back up the reef wall, we were able to remain and follow the progress of this awesome predator, restricted only by our no-decompression limit. Back on the boat after our one-hour dip, there was no swapping of cylinders for us, just a leisurely break before our second dive.
conclusion This course devolves a lot more responsibility to the instructor than is usual for PADI. Surprisingly, from an agency renowned for its excellent manuals, it has chosen not to produce one for this course, relying instead on the Draeger-supplied owner's handbook. This is more of a booklet, written in dual languages, than a dedicated learning aid - and far from ideal. Red Sea Diving College thought this so amiss that it has produced its own manual for students' future reference, and has submitted it to PADI for possible adoption. Additionally, PADI has no final exam by which to assess whether the student has acquired the necessary understanding to use this fairly complicated machine safely. The knowledge review in the instructor manual, although a good learning aid, is not really sufficient as a stand-alone assessment tool. Again, Red Sea has produced its own version. To see whether the lack of the usual support materials was really an issue, and assuming that the world's biggest diving organisation would be up to the mark with safety statistics, I checked with PADI to see what the record was like with this course/equipment. Unfortunately, it had no data on this subject at all. As for the 'would you want to bother?' question, I think probably not. The advantages of SCCR over a large cylinder of nitrox are not, in my opinion, great enough to warrant the initial purchase price, the hassle of set-up and DiveSorb handling and cleaning. Judging by the comparatively few Dolphins that you see about, it would seem that I am not alone in that judgment. The Dolphin might make a good stepping-stone for someone contemplating diving with a fully closed unit, however, as the buoyancy characteristics are similar, and I am sure that the bonus of breathing warm gas will appeal to some UK divers. If you want to give it a go, you could do worse than pick the warm waters of the Red Sea. My course was thoroughly taught by Terry who, in going to the trouble of creating extra material, ensured that I had absorbed the relevant information. Not all instructors would go to these lengths. Judging by the dog-eared material, I don't think it had been produced specially for me! I enjoyed the experience. It was different and, should I get the chance to use an SCCR again, I would certainly do so. Perhaps now that the Inspiration is making inroads into the US market, we can expect to see a fully-closed-circuit version of the course from PADI/DSAT in the near future?
Chris Boardman travelled courtesy of Goldenjoy Dive/Libra Holidays (www.goldenjoy.com), with flights from Gatwick, transfers and a week's B&B at the Hilton Sharm Dreams costing from £479 (£498 from Manchester). A 10-dive package with Red Sea Diving College (www.redseacollege.com) costs £145 and its Draeger Dolphin course costs around £256 + £17 certification fee. The course takes a minimum two days, with any extra days' teaching around £25. Dolphin hire is around £57 per day, including boat fees and CO2 absorbent.
Practising mask removal while swimming - remember, breathe through the mouth!
filling the scrubber canister
Surguei stops smoking long enough to check the hoses
Terry looks over the assembled unit on deck
RED SEA PARTING - WHAT'S THAT ABOUT?
A huge volcanic eruption on the Greek island of Santorini in 1600 BC appears to have generated a gigantic tidal wave. The effects of this 'mega-tsunami' would have been felt across the Mediterranean as far as the Nile delta.
Computer simulations indicate that a 180m-high wave travelling at 400mph would have been generated, the most devastating tsunami in history.
This event could explain the description in the Book of Exodus several centuries later of the parting of a 'sea of reeds', or a shallow marshland, into two walls of water, which were said to have swallowed up the Egyptian army in its pursuit of Moses and his people.
A 'mega-tsunami' could have syphoned billions of gallons of water from seas, rivers and lakes to create dry land for as long as two hours, according to tsunami expert Professor Costas Synolakis.
A similar, though far smaller, phenomenon was witnessed as recently as 1994 in Mindoro in the Philippines, when an earthquake resulted in a tsunami.