Caporegime
What I'd prefer to you would be a small monopod with a tripod mount (can make yourself easily if you don't want to buy the GoPro one)... as long as you can find a monopod that would be ok with a bit of water... can't see a problem.
The trouble with the wrist housing from what I've read is it's a bit limited to the direction you can have the housing...
I see, hmm. Maybe a small cheap monopod (ultimately saltwater kills everything so might as well get as cheap as possible) would be better with a lanyard/wrist attachment of sorts so if I need to use my hands I can drop it and not let it go to its doom.
I feel a homebrew mount coming up