It's a lot of fun, Straight lines are for amateurs though. we had a 3 mile course with 6, 90deg turns, now that's fun! Who cares if you sink! Just shut em down before they go under, purge all the water once you get it back on dry land and you are good to go. We've run sleds off the show room floor before and sunk them 3-4 times in the same day and they are still running around just fine. Skidoos are the best on water, bone stock, then Yamaha (2 stokes only!), and I wouldn't even bother with the Polaris, don't know why, just found that they take on too much water and the belts get wet too easy.
I've got some great footage from races years ago, just never bothered putting it online.