Get that jetski to a SeaDoo mechanic right now!
If water has gotten into the motor anywhere, it's already started rusting and siezing up. I know from experience.
Likely the mechanic will pull the plugs, turn the engine to see if water blows out. My '96 GTX blew about 2 gal. of water out the pistons and exhaust before we got it running again.
Let that water sit in there more than a few days and you may not get it going again.
In case there's no motor damage, my short answer would be to get it on the trailer and pull the drain plug(s) at the back of the hull.
kdcoldiron, July 2009