4) A written report from Frik Henning, Standby diver on boat, was received on 10/07/98 and has been incorporated into this report.

5) The Proposed Dive and Dive Plan

The Dive was one of a series of Trimix deep dives held during the week to further knowledge of the layout and marine life in Wright Canyon, a steep depression in the sea bed. The bottom on the edge is sandy and virtually flat at about 90m depth. Rehan and his buddy were to make an excursion to the 140m mark, to do a visual comparison of the sea life at that depth as opposed to higher up and collect a few specimens if possible.

Johnny decided, prior to the dive, not to descend to that depth and it was agreed he would remain near the edge at a maximum of 120m and act as a deep cover diver instead. The Dive Planning sheet is available on request.

Decompression was to be done while drift diving. Each deep diver was to inflate a long vertical tubular marker buoy at 40m depth and release it, which would be the signal for a dedicated cover diver to descend and check that all was well. He would then accompany the deep diver as he reeled himself up through his decompression schedule. If the divers drifted apart during decompression, there was a dive boat available to follow each of them individually.

Everyone’s first stop was at 40m. Thereafter, the Deep Team’s next stop was at 33m and Johnny’s stop was at 27m. Allocation of the standby divers was as follows:

Rehan - Andries; Peter - Johan; Johnny - Frik.

6) The dive commenced at 13h50hrs on a clear sunny day. A cold Force Four NW wind, which had not been present on previous days, was raising a 1m chop on the surface and creating a 1,5 - 2,0 knot current. Surface temperature was 24^oC but viz had been reduced to 8m.

On the bottom there was no current, only a barely perceptible drift. Although light levels were low, visibility was in excess of 30m. As each diver had torches, keeping track of each other was not a problem.

As Rehan bailed out into the water, he apparently bumped his head on Johnny’s bottles, but on enquiry claimed he was alright. The deep team then submerged.

7) Rehan’s Equipment

2 x 12 liter 220 bar cylinder, connected by a Genesis-type manifold (independent taps, but no isolation valve), filled with bottom mix, Dräger Nemo + Spiro Arctic + inflator hose + BC hose to backup BC + contents gauge

1 x 7 liter 200 bar cylinder, strapped to twin, for Nitrox 32, Spiro Arctic + contents gauge + BC hose to main BC.

1 x 10 liter 200 bar cylinder, filled with Nitrox 80, Sherwood? + contents gauge. No helmet, one hand-held torch, no camera, small reel + AP Valves marker buoy, crayfish bag, wetsuit + chicken vest.

Note : Position of power inflators not able to be confirmed. See Free-flow theory.

8) What happened? A "best fit" collation of the eye witness reports.

The descent and most of the bottom time went off as per plan and were uneventful. Due to the not quite vertical walls of the canyon, the deep team had been displaced sideways about 7 - 8 m from the vertical. In addition the deep pair had drifted a few metres apart while collecting their specimens.

Near the end of the bottom time, Peter saw Rehan swimming towards him, when he stopped, turned and started swimming vertically upwards. Before Johnny could react Rehan had passed him, looking upwards in a fixed direction. As he was sideways on to Johnny, he did not notice him, but could easily have seen him if he had been looking.

Johnny went deeper down the cliff face to check on Peter and they met at 126m, exchanged signals and commenced their ascent on their planned schedule. They changed from bottom mix (12:60) trimix) to travel mix (Nitrox 32) and deployed their buoys at 40m. They were soon joined by Johan, one of the dedicated cover dives. Johnny soon moved to his planned stop at 27m where he began drifting away from Peter who had stopped at 33m. They soon lost sight of each other as the visibility deteriorated above the thermocline at about 50m. Both he and Peter completed their schedules and surfaced without incident.

Back on the boats, everyone was keeping an eye out for the marker buoys, which were expected any minute. Thus when Rehan himself surfaced he was spotted immediately. All agreed that it was a controlled ascent - no rush of bubbles, no rising to his waist out of the water and no unduly inflated ABLJ. Distance estimates from the various boats vary from 30 - 50m He signalled in a calm manner to be collected and shouted for more oxygen and "gas". Witnesses disagree as to whether he spoke English or Afrikaans and whether he called for air, gas or nitrox. All agree he was calm and controlled. Frik’s report states that Rehan shouted "I have had a free-flow. Go to the beach and fetch oxygen.

The boat arrived within seconds and two fully kitted dedicated standby divers jumped in the water, one of whom, Frik Henning, carried an extra side-slung bottle of oxygen apart from his set filled with Nitrox 32. It was for this reason that Frik jumped in as well as Andries, as Andries was not carrying oxygen. Rehan then disappeared beneath the surface in an apparently controlled descent. His surface interval was estimated at between 30 seconds and two minutes. No-one has a clear recollection of whether he submerged before Frik reached him or whether they went down together. Frik’s report simply states that at 6m he offered Rehan oxygen but Rehan chose the Octo and signalled for them both to descend.

Andries Prinsloo, the other dedicated standby diver who had baled out over the other side of the boat, swam under it and was hit by it due to the choppy wave action. The blow was enough to distort the plastic frame of his mask, which created a copious leak. Nevertheless he descended to 20m where he saw Rehan and Frik holding onto each other and descending rapidly. Andries then aborted his dive and returned to the surface.

Rehan was hanging on to Frik’s BC with both hands, and by keeping his elbows bent, had minimised the distance between them, presumably to relieve any strain on the octopus hose. Unfotunately this position prevented Frik from reading Rehan’s pressure gauges. Rehan and Frik repeatedly exchanged "are you OK" signals on descent.

They rapidly reached 40m, at which point Frik showed Rehan his depth gauge. Rehan then handed over the marker buoy and reel and signalled to Frik that he should inflate it.

Frik then gripped Rehan round the waist with his legs, in order to free his hands, and started trying to inflate the buoy. This of course prevented Frik from finning and would have accelerated their descent rate. This buoy is an open ended tube (with a butterfly valve in the open end) about 2 metres long which is normally filled from an accessory filling hose attached to one of the regulator first stages. This option was obviously not available to Frik. While busy, he became aware that he had suddenly become dizzy, stopped what he was doing and checked his dive computer which read 65m. He showed Rehan the reading. Rehan looked shocked and immediately signalled that they should ascend. It is possible that Rehan started finning and of course exertion would precipitate unconsciousness. Frik immediately commenced inflating his BC. Frik remembers Rehan staring at him wide eyed before he (Frik) passed out. His next recollection is waking up on the dive boat.

From the medical team’s viewpoint Frik surfaced in a highly agitated state, tangled in Rehan’s marker buoy, and virtually incoherent when questioned. He was helped into the boat, put on oxygen and checked out by Dr Brits. A check on his decompression meter by the medical team showed that his maximum depth was 65,2m.

9) What went wrong? - An analysis of the eye witness reports

The trigger incident that caused Rehan to abort his dive and shoot to the surface could have been either a free-flowing regulator or (less likely) an out-of-gas situation. The free flow would not have been spectacular as there was very little gas left anyway at the end of the bottom time. It would however have dumped very quickly for the same reason.

From previous discussions it was clear to others (inter alia JvdW) that Rehan was well aware that one of his regulators was near its limit, and that he was anticipating a failure.

His apparent abandonment of his buddies is no mystery. Rehan had often expounded his twin philosophies that a) each deep diver should be self-reliant and not dependent on his buddies and b) that you could in practice switch to travel mix at any depth because you reached its safe depth before its toxic effect could become apparent.

What is certain is that he did not panic but put into action a pre-planned escape plan. From records kept by boat personnel, Rehan took at least six to seven minutes to surface, where he arrived calm and controlled. But the early change-over obviously ate heavily into his reserves of travel mix. It is not impossible that he deliberately slowed his ascent, using all his reserves in the process, so that he could out-gas as much as possible before being forced to the surface.

Having made a text book ascent and made his needs known, the next logical step in his revised dive plan would be to get down to his first stop (40m) as soon as possible to resume his decompression. So probably without realising the consequences, he must have vented the entire contents of his double BC. Only after he had descended a few metres would he have discovered that he had absolutely no breathing gas left, apart from his oxygen. This would be more than sufficient to fill a BC even if he had only started inflating at 10m depth. The evidence shows that he did not inflate either BC which implies he could not.

10) How could this accident have been prevented? assuming no changes to the existing dive plan, equipment and personnel.

The accident sequence we have postulated above has an awful inevitability about it - and in truth Rehan had very little room to manoeuvre. There are three possible courses of action that may have helped :

a) Inflating his marker buoy on the surface from his oxygen bottle and then reeling himself down to 40m. This may have provided up to 10kg of lift. Similarly inflating Frik’s BC earlier may have limited the overshoot and bought them more time.

b) Taking a few deep breaths from his oxygen bottle, and later the octopus regulator, and attempting to inflate his BC’s orally. This of course sounds easy on paper, but may have been very difficult in practice. Rehan may have built up quite a severe oxygen debt before the standby diver arrived with the Octo. Fluffing an oral inflation attempt under such conditions would have instantly compounded all his problems. Hanging on and getting his breath back first would have seemed the more sensible option.

c) Ditch his whole expensive rig at 40m. Doffing and Donning is hardly part of Technical Diving Training but this option may have occurred to Rehan given enough time. Even then, once attempted, a hangup may have occurred between the ditched rig, the marker buoy and/or the standby divers gear, giving the potential for a double fatality.

11) Conclusion

It would seem "obvious" then, that the direct cause of the fatality was breathing Nitrox 32 below the safe depth. How this situation was arrived at can never be determined for certain despite being satisfied with constructing a logical "best fit" scenario that does not clash with observed "facts. This scenario suggests that the trigger incident was probably regulator failure (free-flow), which was compensated for in text book fashion as shown by Rehan’s controlled arrival at the surface. The indirect cause of the accident was Rehan’s inability to attain, and maintain, neutral buoyancy at his desired deco stop.

It is also clear that this was not due to simple failure of equipment or personnel at that stage of the dive. This means that future Technical Dive Planning must be thought through from first principles to take the circumstances outlined above safely into account.

12) Note