You're actually better off doing it standing. (I used to be a diver and now I coach). Start off with "penny drops" where you stand on the edge of the pool, do a complete circle of your arms, and jump when they get to the top. While you're in the air, work on keeping your arms right where they are and bringing your toes to touch your hands. You should land on your butt/lower back, but done properly it wont hurt. (also when you're starting, jump further out so that you dont hit your head). Once you've mastered penny drops, start touching and looking back for the water (this is a reverse dive pike). After you get the feeling of this, try doing it tuck (you'll spin a bit faster. A gainer flip is basically a backflip travelling forwards, so doing backflips can help. Also if you have a trampoline, put a piece of tape on it, and stand on the tape. Practice backflipping and trying to land in front of the tape (that's also a gainer flip). This trick is all in your arms, NOT your hips. Greg Louganis threw his hips forwards instead of using his arms, which kept him over the board on gainer 2 1/2, which is why he hit his head. Truly, the most important piece here is your arms, they will make or break this dive. If you have any questions, feel free to PM me. Also, I realize that some people's egos wont let them take advice from a Newb, but being a varsity diver for 8 seasons kept me off the slopes and I'm just getting back into it.