Sorry to disagree with the above poster, but I took my camcorder on the water rides. I have a small digital one with a nice strap that I wrapped around my wrist a few times so that if it did slip, it wouldn't hurt anyone. I also placed a zip lock bag over the camera. I did film the water rides in parts and pieces, here and there and some of the drops. The zip lock bag did get wet on Kali and Splash but the camera was dry underneath. It is all in the planning.
I also would advise for you to think a little about what you want to get on tape for future reference. If you want a certain ride on tape, then tape it if possible from start to finish. You can always edit it out at home if you find it boring or overly long. I filmed most of what I could get of Spaceship Earth due to ongoing rumors of a possible new ride going in. I just truly wanted to preserve that moment as I never got to with Horizons before it closed.
Definately do a little thinking about before you go. Also tape preshows if you know you enjoy them. I got 4fora$ before the B&TB show. I then taped all of the beauty and the beast show while my camcorder sat on a wall. Picture looks great and as I wasn't holding the camera, no shaking. However, I just let the tape run and didn't do any close-ups which after reviewing it at home would've made a nice touch. I have really nice shots (ie. approaching MK on ferry), beautiful shots (castle and various animals in AK), gorgeous shots (spectromagic and Wishes) and some not so hot shots (PoC, one or two in Spaceship Earth). I also have action film from Splash and Test Track. Just remember, take plenty of film and you can always edit things out later.
Have fun making great memories.