I have played with these on computers and I think it would work well for a seadoo. They only use around 5amps which is the same as a atwood turbo fan.

http://cgi.ebay.com/Peltier-Cooler-T...QQcmdZViewItem

It could be placed against a blue ice pack and mounted to a hold cut in the intake tube. Then on the hot side you could either run a water tube from the intake water, use a low voltage fan with heatsink or just have another air intake blowing on it.

This would put about 30 celcius or -22 farhenheit into the air intake. I bet you could get 2 or 4mph and it would be all day.