i saw one where they cut off a peice of one of those foam pool noodles and tied a string through the middle tube part and then through a bar mount. cheap and easy. you could also just use a chest mount or wrist mound
on second thought, if you have a camelback, try putting a stick up from one of those. they are small enough to swim around with and whatnot. they are very ajustable and you can probably mount a gopro from there and do cool flips n shit
Put a string through the mounting holes on the bottom of the enclosure, then put that around your wrist. Duct tape a piece of a pool noodle to the pack so it floats.