While that stuff is pretty hard to do, and i know because i used to do it, not that good, but all the same... it really is all about timing and using the skis power at the exact moment. In reality you do more work riding a wheelie on a bicycle than doing some of the basic stunts on those jet skis. I used to like to pop up and dive under the water about 5 or 6 feet then come back up like 25-30 feet away... that one never gets old
Funny story, i was nose diving my dads Raider 701, and after getting back to the dock, a whole bunch of water was coming out of the drain plug holes so we popped up the hatch and the engine compartment was FULL of water. Turns out that the air vents of the engine compartment were hidding behind the mirrors and everytime i went under... water everywhere. That was the last time i ever did that lol.