pentax optio w30 works good for me. not really tough, but its survived a few droppings but I wouldn't expect it the take constant abuse. I keep it in my chest pocket on a lanyard. waterresistant - rated for hours at up to 20' deep I think.
"Remember, my friend, that knowledge is stronger than memory, and we should not trust the weaker" - Van Helsing
i jsut use my regular camera (its an old clunker any way) or the one on my phone.. its risky buisiness.. if you are out there..
just get an old cheap one. $50 or so. something you are willing to risk losing to the water. that plastic bag idea is a good one too if you plan on chest highs all night.