I use my phone whilst waterskiing... well, I have it with me when water skiing anyway. it sits in an aquapack, which is basically just a pvc bag with a sealing top. in fact, I've put a camera in it before and submerrsed it totally down to 2m.
now no matter how much a seadoo flips, it will not go down 3m... if it does, then whatever happen would probably kill you!
Anyway, using some ****ty pvc, the unit can be sealed. but cooling will be another matter all together. I suppose you could do this however:
make all heat transfer to a single point (using heatpipes if you have to) and seal the seadooter with PVC. Just at the part where you've compounded all the heat, make a hole in the pvc and mount an aluminium/brass heatsink. imagine a car amplifer look. so the top would be the heatsink, and the bottom part would be entirely sealed. That way, you can mount the pooter (and you'd better mount it solidly) somewhere where there's lots of air, and be safe that air and water the pass it will only cool it.
h/d usage will not really be feasible. you can try, but I think it's pointless. u'd probably need some solid state.
for the touchscreen, that's easy to seal also using the same technique. like I said, I've gone under water with an aquapac with my pocketpc and camera, and they're both fine.
that's the theory... now... what the hell do you need it for?
