When I went through survival school with the USAF, they mentioned that if you were getting sea-sick on the emergency raft, to slide over the side and float in the water. Apparently that has a calming effect on you, and the sea-sickness goes away. Granted, it's considerably easier to do this over a life raft than it is a larger boat/ship.
It has a calming affect on your buddies knowing you will not throw up in the raft all over them. Besides, the sharks rubbing against your legs takes away from your worrying about throwing up.