In May 1973, eight divers attempted a deep dive in The Shaft, a dangerous sinkhole in Mount Gambier, South Australia. The cave had a narrow entrance leading to a massive, deep underwater chamber, and its full depth was unknown at the time.

During their dive, the group pushed deeper than was safe, using only regular air instead of specialized gas mixtures. Nitrogen narcosis, poor visibility due to silt, and unexpected cloud cover confused. Some divers lost their way, with four—Christine, Gordon, Stephen, and John—never resurfacing. The survivors desperately tried to find them but had to abandon the search.

Authorities attempted multiple recovery efforts, but the extreme depth and lack of visibility made it nearly impossible. It wasn't until months later, when a film crew was shooting a documentary, that Stephen’s body was accidentally discovered at just 50 feet. Police later retrieved him, but the other three bodies were never found.

This tragedy highlighted the dangers of unregulated cave diving and led to increased safety protocols in the field.