In 2004, Dave Shaw, a professional commercial pilot and sometime deep cave diver, found the body of Deon Dreyer - a young man who had been dead for nearly 10 years; the discovery was made at a depth of roughly 300 meters, at the bottom of a huge cavern known as "Bushman's Hole" in South Africa. The parameters of Shaw's dive plan didn't allow enough time for him to bring the body to the surface, but he was determined to assemble, and return with, a recovery team, a commitment that would ultimately yield tragic consequences.
There is a lot of technical information in the book, especially relative to advancements in diving apparatus and gas mixtures. Finch explains, in detail, the options available to divers at various depths - and the possible ramifications of their choices. He painstakingly describes the effects of depth and pressure on the body, how different mixtures of helium and oxygen affect breathing and carbon dioxide levels, the hazards of nitrogen narcosis, and the value of a good decompression plan. He also provides a view of Shaw's personal life, his marriage and family, and that of the other members of the recovery team, most notably his friend Don Shirley.
Precise planning of the "big dive" was crucial and meticulous; each team member had a specific submersion time, calculated to the minute so he could provide support along the drop line, and each had his own depth limit and dive time, based upon personal experience and training. Many earlier dives were made to position emergency gas/air cylinders along the decompression route. A few minutes on the bottom at such an extreme depth requires a laboriously slow return to the surface, over a period of 10 or 11 hours. Medical staff and police divers were on hand; a pulley system was designed to transport an injured or "bent" diver from the surface to an on-site decompression chamber. It's like a carefully choreographed ballet.
Finch fully explains the hazards - and that nothing is certain - at such depths. And in such a critical sequence of actions, it only takes one flaw, one brief error in judgement, one deviation from routine, to create a disastrous ripple that leaves one friend dead, the other struggling to survive during a 10-hour crawl back to the surface. The action is churning, suspenseful - and the loss, and sorrow, palpable.
But Finch also describes the allure - the awe, the amazement, the euphoria that comes from seeing something rare and beautiful, and going to places that most cannot even imagine. For the deep cave diver, those things overshadow the dangers. Very interesting, fascinating reading.