Dunkinin the dark
Theres diving, theres free-diving and theres dunking - thats when youre dumped under water in a container and have to make your own way back to safety. Its all for your own good - Monty Halls goes along to watch

Drive through the gate at the Royal Naval Air Station at Yeovilton, Somerset,and you will be directed to a redbrick building next to the manicured sports pitches. Its exterior betrays nothing of what takes place within, except for a single discreet notice informing you that you are standing outside the Underwater Escape Training Unit.
     Once inside, things become slightly less subtle. The first thing you see is the pool, 4m deep and 12m across. Suspended above it is what appears to be a large blue barrel, sprouting an ominous collection of hydraulic cables connected to a robust metal frame.
     Beyond the tank, on the far side of the pool, hangs a banner. This gives the game away, letting you know precisely what this building and the gently hissing barrel are all about. Letters a foot high read: Self Determination - Now!
     This unit, known affectionately as the Dunker, is an essential part of training for any military personnel involved in flying in helicopters over water. As I enter the building, a platoon of Royal Marines recruits is lined along the viewing platform, eyeing the Dunker suspiciously.
     I remark to Warrant Officer Des Enoch, chief instructor at the unit, that he must witness some emotional scenes. The comment raises a wry smile.
     The ironic thing is that the longest anyone in the Dunker will be under the water is about 20 seconds, so in effect what were asking them to do is very easy. Its only when you add the intense disorientation they will experience, put them in complete darkness, and demand that they exit the module in a disciplined manner - thats when the fun can really start.
     The Dunker has been in operation for 16 years and there has never been a serious incident in that time, so its clear that safety is a key factor in the drills.
     This doesnt stop Des describing enthusiastically the less serious incidents that occur occasionally, from disorientated trainees trying to claw their way through the metal floor of the module, to six people trying to get out of the same small hatch at once.
     Two modules are available for dunking, one replicating a Merlin, but today we will be using the smaller Lynx, with eight recruits crammed into its murky interior for each exercise.
     For Royal Marines recruits, four phases of dunking are required to achieve a pass. Aircrew must perform two extra phases during which they use STASS (Short Term Air Supply System). Our recruits will not have access to such equipment in the event of a real dunking, so their drills are based around taking a single wide-eyed breath as they slip beneath the surface.
     The first phase is a straight dunking in full light. This is followed smartly by an inverted dunking in full light (the unit flips over after entering the water).
     Having lured the occupants into a false sense of security, the final two dunkings take place in semi-darkness, and then in a black-out. This final run is an apocalyptic affair, with the unit flipping as it enters the water, the lights cutting to plunge the pool into total darkness, and the ensuing exit from the module lit only by strobe bursts designed to simulate shorting electronic circuitry.
     The first group of recruits is ordered into the water to paddle, ashen-faced, towards the module waiting for them in the centre of the pool. One wears a red helmet, in contrast to the yellow helmets of the remainder of the group.
     Des is quick to enlighten me. The red helmets indicate a weak or non-swimmer, he says. We generally keep a pretty close eye on them.
     I remark that to put a non-swimmer in a small metal can, plunge him into water in complete darkness, spin him round and expect him to claw his way to the surface is rather a tall order.
     Des looks thoughtful for a moment. Yes, I suppose it is. Its surprising though - weve had non-swimmers breeze through, and hairy-chested gladiators go ballistic the moment the Dunker hits the water.
     Its almost impossible to know how an individual will react.
     It seems, however, as though this run will revert to type. The recruits are taught to orientate themselves within the Dunker by gripping something within the cabin thats in line with their point of exit. When the lights go out and the world is upside-down, they follow their arm and, presto, theyre swimming to the surface. Such techniques have saved many lives over the past decade.
     As the Dunker enters the water, pausing briefly at the surface, I cant help noticing that the hand gripping the edge of the door of the module possesses some porcelain-white knuckles.
     This leads me to make the (correct) assumption that on the other end is a red-helmeted recruit wondering why he didnt get a job in a bank.
     The first run sees the module settle several feet under the water in a cloud of hissing bubbles. There is a pause, then the Plexiglas hatch covers are thumped from the exits, and the recruits stream to the surface. Last out is a flailing figure in a red helmet, exploding from the cab like a cork from a bottle.
     By the time the safety diver has checked the interior, and the Dunker is being hoisted back to the surface, the recruit is sitting on the edge of the pool with an instructor gently persuading him to get back in for the second run.
     To his great credit he does, and the second run sees him scrabbling his way to the surface in a similar manner. By this stage Im surprised that he doesnt splash his way to the edge of the pool, climb out, and wordlessly march to his nearest job centre.
     Miraculously, however, after a word or two from his training team - Remember who you are and who you represent - he dog-paddles back to the cab for the final two phases, disappearing into the interior after a wistful (and in his mind presumably final) look at the outside world.
     The third phase requires considerably more discipline. The lights are out, disorientation is total, and the recruits must exit the cab in a set order. In some cases this means sitting tight while others climb over the top of you before making your own escape.
     This results in an ordered stream of recruits exiting from a single window, in the midst of which is our red-helmeted gladiator, presumably rather more philosophical after accepting imminent and inevitable death on the final run.
     The final run is every man for himself. It takes place in total darkness, and the module fakes a roll one way before tumbling the other as it enters the water. In pitch blackness it settles below the surface, and a moment later the doors explode off the casing, closely followed by a bomb-burst of several recruits.
     Enthusiasm is the order of the day, and within seconds the casing is empty and the recruits are moving towards the edge of the pool, red helmet bobbing triumphantly in their midst.
     Id say were the premier facility of this kind in the country, and our role in training our personnel to cope with the extreme stress of an aircraft dunking in the open ocean is critical, says Des, when I ask him to summarise the role of the Dunker in flight-safety training.
     Since the Dunkers inception in 1987, the response of aircrew and passengers unfortunate enough to experience real ditching incidents indicates that Dess statement is no idle boast, and that the reputation of the facility for providing realistic and strenuous training is well founded.
     A glimpse of a stricken face beneath a red helmet speaks volumes for the fact that, short of crashing a helicopter into a real body of water, the Dunker is a pretty good substitute for the chaos and confusion of the real thing.

This must be the place
Breaking the surface - ah, what relief!

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