Cave diver suffocated

Experts say Australian diver Dave Shaw, who died in Boesmansgat earlier this month while trying to retrieve a body, probably suffocated.

Shaw, 50, was trying to bring the body of 20-year-old Deon Dreyer, who died in the cave ten years ago, to the surface.

Their bodies were unexpectedly pulled from the depths of Boesmansgat as divers raised equipment attached to a line.

Post mortems have been done on both bodies, but police spokesperson Ernst Strydom says they haven't yet received the results from the pathologists.

However, doctors involved in the fateful dive on January 8 have already posted their findings on the website of the International Association of Nitrox Divers.

The doctors
- examined the actual diving equipment;
- analysed the gas mixtures used;
- critically reviewed of the video footage from Shaw's camera;
- re-enacted the breathing patterns on the Mark 15.5 re-breather to capture the last 10 minutes of the diver's life and
- re-enacted the orientation of Shaw in relation to the body and the associated equipment.

They say Shaw successfully reached Dreyer's body, but was unable to recover it due to a number of unforeseen practical factors.

He appropriately aborted the attempt at six minutes - as planned - but subsequently became entangled in the line previously used to mark the body.

In his effort to free himself he succumbed to the combined effects of carbon dioxide build-up and nitrogen narcosis.

The doctors say they are certain that Shaw drowned after becoming unconscious, about 22 minutes after going underwater.

They say evidence suggests that Shaw suffocated.

"Overfilling of his re-breather appears to have prevented him from exhaling properly.

"The breathing impairment, combined with the increased activity of recovering the body, led to a critical build-up of carbon dioxide over a period of 10 minutes.

"This is sometimes called 'deep water black-out'."

"David became increasingly incapacitated, eventually lost consciousness and ultimately drowned.

"While relatively swift, the duration of the process favours carbon dioxide build-up as a cause rather than a lack of oxygen.

"Nitrogen narcosis may have significantly interfered with his ability to solve the problem before it was too late.

"Once he lost consciousness, drowning became inevitable.