If I were you, for anyone whose scripting, Keep it simple, and not full of a ton of useless things.
Well, I would use a script to keep it level, use Spacebar(Jump) to elevate, and Shift(Crouch) to decend. If there's a script to keep it level, then this should be no problem. Also fires torcreeps?
Then you could go right over water.
Make it a bot, and when you crouch, it goes under water, and the water should make it float, thats the simpliest thing you could do, instead of these hacky up downs where people can just fly out of the water.