On May 28th 1973, in the worst cave diving tragedy in the world, four divers out of a party of eight drowned in The Shaft, one of the largest sinkholes known in the Mount Gambier area.

The eight divers entered the water with a general plan to descend to a depth of 60m, to take photographs for the promotion of a Sydney dive shop. One of the party was reported later as saying that "they were just going to do a bounce dive to 250 feet and back again", hardly a rational dive plan.

A vertical shotline was rigged from the surface to the top of a submerged rockpile 35m down. The group of eight then descended in no particular order to the planned depth of 60m when one of the divers who felt unwell returned to near the surface, signalling to some of the others as he did so. Feeling better, he descended again several minutes later and saw some of the others by now ascending so he joined them. When everyone gathered on the lake surface they found only four divers, not eight. Descending again separately, two of them were unable to locate their companions but found a torch and a camera on a rock at 60m. The police and ambulance were then alerted by the others.

At the inquest three months later, the coroner found that all four divers drowned as a result of running out of air due to their overstaying their time in the sinkhole. At that stage, none of the bodies had been recovered despite several police searches, and this conclusion was based on the evidence available. But when they were eventually found some months later, there was some air remaining in their tanks. Again the effects of nitrogen narcosis prevented them from thinking rationally when they needed to extract themselves from the dangerous situation of such great depth.

In fact, from what we can judge, these people died of sheer fright. Their bodies were found under a flat-roofed tunnel-like section with a silt floor, just back out of sight of the shaft of daylight. Thus they were unable to see their way out, just at that time when they realised that they would have to ascend for deco stops. In the confusion, four of the party did not see the flashing torches of their buddies at the tunnel entrance, who could see the daylight but had no bottom time left to chase them.

The coroner also found that:

• there was no dive leader or coordinator, and lack of a useful dive plan
• no spare tanks were suspended from the shotline for the divers to decompress after such a deep dive
• not all divers even had depth gauges
• " . . . despite allegations that they were experienced divers and four of them were qualified instructors, including two of the deceased persons, . . . none of the group was an experienced sinkhole diver and that no proper safety precautions were taken, . . . nor did they have a 'buddy' system or any other recognised safety system."
• " . . . the allegation that the deceased met their deaths as a consequence of having inhaled impure air supplied to them (by the shop in Mount Gambier) is entirely without foundation."

Later post mortems, after the final recovery of the bodies, showed that the immediate cause of death was by drowning and that any question of air contamination was completely ruled out. It was found that the victims died as a result of going far too deep without regard for several fundamental safety procedures which some of them, as qualified instructors, should have known through teaching others.

As a result of this accident, the landowner has denied permission to dive in this finest of sinkholes, which is in fact a safe and predictable dive if basic safety rules are followed. There was no need for the accident, and is no need to place this world-class dive off limits to sensible and adequately trained cave divers.

Accident Analysis
Cause of Death - drowning after running out of air
Major Contributing Factors - inadequate training, inadequate equipment, diving too deep on air, failing to run a continuous guideline

More information on The Shaft

The Shaft Map | Credit: Tim Payne