there's quite a few choices. I have two Go Pros, the original and the HD. Both are fine though a bit limited. The HD's wide angle lens makes the whole world kind of round. I really like the option of automatically shooting a photo every few seconds. It's good for building animoto slide shows or just catching action shots when you can't use your hands. Lots of mounts for the gopro too--head mounts, chest mounts, deck, paddle, etc.
If you want better lenses, zoom and and more features the Sanyo Xacti series is good, The cameras are waterproof to about ten feet (though I've had them much deeper. Unfortunately you need to have the screen swung out to shoot--stupid requirement, but there you go. You can mount them with any tripod mount.
For a bit more money (around 500) you can get a panasonic Lumix TS2 which is pretty bulletproof. Shoots HD 720 video, 15 megapixel photos with 4X digital zoom and image stabilization. Very tough camera. My friend Bill Boyum here on Maui has one that he's used to shoot some amazing downwind videos
I just bought a Sony Nex-5 that I'm going to get a waterproof case for. It's kind of a semi-pro step, a lot of camera for not so much money (under $1000 for everything). Interchangeable lenses, HD video, huge sensor, shoots 1080p at 60FPS. Overkill for most stuff but I'm trying to shoot some semi-pro video for my websites.
I'm working on an xtreme camera review on one of them: Xtreme Geezer (
www.xgeez.com) but it probably won't be up for a few days.