Bushman's Hole may seem unassuming on the surface, but this cave in South Africa's Kalahari is one of the world's deepest freshwater cave systems, attracting seasoned cave divers from around the globe ...

He had spent decades rewriting the rules of deep diving, surviving narcosis, near-death rescues, and caves no human had ever seen. But at 305 meters, in a sinkhole so deep it swallowed light, the ...