Sinkhole that opened up in man's paddock killed four people who went to explore what was underneath

A ‘bottomless’ sinkhole discovered in 1930s Australia has tragically claimed the lives of four recreational scuba divers, and now only the elite are allowed to explore its depths.

At first glance, third-generation farmer Trevor Ashby’s dairy institution near Mount Gambier, South Australia, looks like a typical strip of land, with loitering cows and animal paddocks.

But underneath the ground is a stunning cavern, described by experts as a ‘bottomless pit’ which is thought to be around 394 feet deep.

This underworld, known commonly as the deadly Shaft, was discovered way back in 1938 when a confused farmer wondered why his horse had almost fallen over in their field, as per the Daily Star.

The sink hole is known as the Shaft (ABC Australia)

It’s understood the cause of the disturbance was a small patch of land, and explorers have been itching to visit the site ever since.

“We really didn't have a clue how big it was underneath. We had no hope of filling it up," Ashby told ABC.

"It looks like an ant hill down there, and we've tipped a thousand tonnes of stone down there.”

According to The Border Watch, the Shaft’s main chamber spans 140 meters across and has a width of around 80 metres at its narrowest.

“It is a truly spectacular sight to behold when you are floating at 40 metres and a shaft of bright sunlight beams through that little hole way above you,” Dr Tim Payne, Cave Divers Association of Australia (CDAA) instructor and the Shaft dive guide told the site.

Now, only CDAA-qualified divers are allowed to go into the Shaft (ABC Australia)

Dr Payne, who described the Shaft as ‘one of the jewels of the region’, understands why it’s on the wish lists of thousands of cave divers across the globe.

“Its unique location, crystal-clear water and scale are factors contributing to its status as a premium site,” he explained. “The visibility is such that divers can be seen from end-to-end of the main chamber.”

In the late ‘60s and early ‘70s, the Shaft became extremely popular among thrill seekers.

"We've had people who have dived all around the world and have come to here and they just couldn't believe the size of the room that we've got under our feet here in the middle of a cow paddock," cave diving instructor Gary Barclay explained to ABC.

However, that was until four divers tragically lost their lives when venturing further into the pit.

In 1973, 18-year-old Christine M. Millott and her brother Stephen ventured into the flooded sinkhole with Gordon G. Roberts, John H. Bockerman, and four others.

Christine M. Millott and her brother Stephen were two of the casualties (National Library of Australia)

Unfortunately, the handful of named scuba divers explored the depths beyond their own planned limits and subsequently became lost.

Unable to find their way back to the surface, the troops’ bodies became trapped and it’s thought they may have eventually exhausted their breathing air and died by drowning, a police report stated at the time.

“There was no hope of recovering alive any of the overdue divers from the outset,” the inquiry, written by former Chief Superintendent Wallace B. Budd.

“Almost eight months elapsed before the first body was located and that was only by chance.”

It’s understood the remains of the other three divers stayed hidden in the Shaft before two members of the squad, trained in deep diving techniques by Royal Australian Navy instructors, headed down to rescue them.

Despite how dangerous the chasm is, people can still dive into the sinkhole. However, due to it being on private land, only divers accredited with the CDAA are allowed to adventure.