The seadoo Rxp and Rxt's are good in the ocean b/c they are intercooled (they use antifreeze like cars). The only thing the saltwater see's pumped through the jet drive not the motor like most boats and jet skis that are water cooled.
I used to have a gp 1200 they will flip around on a dime, they are light and really fun.. when they run right. 3 carbs and two stroke ment they were fast, but tempermental when they were not perfectly tuned. Also you have to worry about two stroke oil, and they are veryyy loud. Just some food for thought