90 m under the sun-scorched red dust of the Nullarbor lie some of the world’s largest underground cave systems, spreading mile-after-mile of cold cavernous darkness. These caves have been formed over thousands of years, out of the limestone that lies under the plain. Once you leave the glare of the sun, the caves are awesome. Weebubbie, the main entrance is more like a quarry than a cave, and Cocklebiddy are among the largest tunnels in the world and they lead to enormous subterranean lakes. This is a hot, dangerous remote place to be and is the kind of place people have passed over for years but never explored. The caves you enter are a long way from medical help and some extend over 5 km into dark tunnels, often interrupted by high dry chambers—it’s easy to get lost in.

The preliminary descent into the cave mouth is relatively easy, there are ladders and hoists for your gear and you can still see the sky and feel the warmth coming off the orange rock—it’s once that you suit up and get into the literally crystal clear water and darkness that it gets challenging. Most visitors make it to the Rockpile, a dry pocket about 1km in, and admire the clear water, the boulders and the interesting shapes of the tunnels then turn around, but if you go deeper you’ll see more of the worn limestone sculptures of the earth’s interior. If cave diving is now the world’s most dangerous sport then the Nullarbor caves must be some of the world’s most dangerous places.