I recently stumbled upon this extremely unique and interesting case in the Journal of Forensic Science. Immediately upon reading it, a number of thoughts played out in my mind. First was, this guy had some balls. Perhaps it can be credited solely to the drive of sexual compulsion, but to follow-through on such an elaborate and risky bondage scenario--alone--takes a pair (irrespective of the inherent foolishness). What did he plan to do if something went wrong? Strapped to a board, submerged beneath the waves, with no failsafe... shudder. Even Houdini had assistants!
ABSTRACT: The term Aqua-eroticum was first introduced in 1984 by Sivaloganathan to describe the unusual autoerotic death of a man using submersion as an asphyxia method. This was the first case of that kind, and since then, no other case of autoerotic submersion has been reported, nor other autoerotic fatality in open water. Here we report the case of a 25-year-old man, nude under a home-made plastic body suit, overdressed for the season with winter clothes and restrained by complex bondage. He was submersed, tied underwater to a boat and was using a home-made diving apparatus for air supply. Death was ruled as accidental autoerotic asphyxia from rebreathing, caused by the faulty air-supply device. 
1. Aqua-Eroticum: An Unusual Autoerotic Fatality in a Lake Involving a Home-Made Diving Apparatus. J Forensic Sci, January 2006, Vol. 51, No. 1