If you want real fun in an RC speed boat, this one has all the speed you can get in a Vector RC Controlled Boat.  It is a self righting boat that won't sink if you capsize it.  It sells for $429 on Amazon but you can get this new in box unit for only $350 from Bill's Boat Stuff.
 
Questions?  Call Bill at 573-247-3631.
 
Thanks for looking, and HAPPY BOATING!