A true story of death and survival in the world's most dangerous sport, cave diving. Two friends plunge 900 ft deep into the water of the Komali Springs in South Africa, to raise the body of a diver who had perished there a decade before. Only one returns. Unquenchable heroism and complex human relationships amid the perils of extreme sport.

On New Year's Day, 2005, David Shaw travelled halfway around the world on a journey that took him to a steep crater in the Kalahari Desert of South Africa, a site known locally as Boesmansgat: Bushman's Hole. His destination was nearly 900 feet below the surface.

On 8 January, he stepped into the water. He wore and carried on him some of the most advanced diving equipment ever developed. Mounted to a helmet on his head was a video camera. David Shaw was about to attempt what had never been done before, and he wanted the world to see.

He descended. About fifteen feet below the surface was a fissure in the dolomite bottom of the basin, barely wide enough to admit him and his equipment and the aluminum tanks slung under his shoulders. He slipped through the opening, and disappeared from sight, leaving behind the world of light and life.

Then, a second diver descended through the same crack in the stone. This was Don Shirley, Shaw's friend and frequent dive partner, one of the few people in the world qualified to follow where Shaw was about to go. In the community of extreme diving, Don Shirley was a master among masters.

Twenty-five minutes later, one of the men was dead. The other was in mortal peril, and would spend the next 10 hours struggling to survive, existing literally from breath to breath.

What happened that day at Bushman's Hole is the stuff of nightmarish drama, juxtaposing classic elements of suspense with an extreme environment beyond most people's comprehension. But it's also a compelling human story of friendship, heroism, unswerving ambition and of coming to terms with loss and tragedy.