You'll be surprised how slow they go over if you go on your side. Especially if you are actually trying to go over. You have a few seconds to think about not jumping or falling into the sail, boom, boards, or anything else that would be bad for you or the boat. Sometimes you don't even have to jump off, but can climb down from the top hull. Be careful if your are sailing 2-up, if the other person jumps or falls off, it will shift the balance of the boat and can throw you off.