Hey I remember doin that as well, but we ended up using a huge tractor tube with at least 8 of us teenagers on it, especially when there was a bit of slime on the spillway.
We would all get on it and bounce on it at the top to get it planeing and then we would absolutely fly down! When she hit the water it would bury way deep and then bounce back and hurl us off in every direction.
Awesome fun! great memories.
Cheers