I guess in one sense you're using the water to decrease your speed by dragging your foot, but I think I agree with TBack. Otherwise, I'd carry a drouge and toss it out if I'm early to a start line and need to slow down...
I'm going to install a drag brake under my trampoline. It could really come in useful!
Seriously though, he makes a good point in that it does not appear to be expressly prohibited to put your feet in the water to slow your boat down. I would be interested to hear some sort of official interpretation on this (and my drag brake).
