i can do 180s sometimes, and every time i go to try doing a 360, i dont have enough guts unless we slow the boat right down..... which at slower speeds i dont get any height. i will feel more comfortable trying 3's if i had some tips from people who can do them.
There's your biggest problem. I wouldn't even think about trying a 360 until you have the 180's down solid. It's a night and day difference between the two. It's my opinion that you should spare yourself the frustration and keep working on the 180's.
As Blabel said, if I learn 180's solid before 360's I think I would of had a much easier time. So learn 180's well first (with grabs, etc.) Also, if you have a trampoline around that will help a bit.