mischief, you got two options here. One is to go with a waterproof P&S camera. Olympus, Pentax, Nikon, Canon and Sony all make one. They are dustproof, crash, freeze and water proof cameras. Most of them support high res video now and take decent stills at good light. I've started recording my action videos with Pentax and Olympus cameras. I liked carrying a single camera for all my needs.
Another option is to go with a camera made just for the sport. These cameras are lighter, smaller and probably can take a beating a little more than P&S. The downfall, they don't take very good stills and most of them don't have a fancy screen to preview what you recorded. You basically aim to where you want to shoot and push the button. The good thing about these, they are all very wide lens so you can capture a lot more action in your footage, but only at short distance. I have my camera mounted on a tripod on the stern of my 16 footer and anything past the front passengers is too small to see detail.
I believe the leader in this category be GoPro HD, but other choices are: ATC2K Waterproof Action Cam
, ContourHD 1080p Full HD Helmet Camera
I haven't had experience with these two, so I can't say anything about those cameras. I do have GoPro HD and really like the videos I made with it. If you are interested, PM me and I will give you links to my Youtube page you can see some of the videos. I've spammed this forum with my videos enough already.
GoPro comes with different mounts (suction, clamp, wrist, etc), while a P&S camera you'd have to mount a tripod head on the helmet and attach the camera that way. I've done both and it works. So I don't think you can go wrong either way.