A couple of guys on a Hobie 16 at Ruff Riders last year went one better than a water proof FM. They bought a throw down stereo system from a garage sale, wrapped it in plastic with some kind of power supply (car battery and inverter I assume). They then proceeded to rock down the intercoastal water way, made 80+ tacks out Mansfield cut and then sailed into the Gulf. They wern't the last to finish either!

Chris.