Just came across this and thought I would pass it along,
Aquatic Books, interesting stuff at:
http://www.sfdi.com/newsbookreviews.html
Including;
Beyond the Deep: The Deadly Descent into the World's Most Treacherous Cave
This extremely detailed first-person account of a 1994 expedition will leave you on the edge of your seat. Cave-obsessed Bill Stone spent a good part of his life developing the techniques and equipment needed in order to achieve his goal, exploring the ends of the mysterious Mexican cave system Sistema Huautla, which plunges a kilometer and a half down and stretches out for tens of kilometers. To go the deepest, the coveted "booty" in the caving community, Stone developed a special rebreathing apparatus for swimming through submerged passages called sumps. A taskmaster, Stone assembled an eclectic team of fellow hard-core cave divers and continually pushed them harder and harder. Stone's team, including then-girlfriend and co-author Barbara Am Ende, constantly get themselves into death-defying situations that lead to injury and finally the death of a friend. Photographs, drawings, and maps abound throughout this extreme adventure story. You will learn much about caves and cave diving, including history and techniques, if you can wade through the technical jargon. The story is very exciting, but it is easy to get lost in the details. Hang in there and finish the whole book to read of their eventual success; it is well worth the effort.
The Cis Lunar MK5 Rebreather, there was a time when I wanted one of these in the worse way?!