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.
Funny you should say that. When I went through the water survival part of the training, I went to Homestead AFB, FL (early 90s). The area we used was Biscayne Bay. They told us prior to going out into the water that Biscayne Bay was the hammerhead shark capital of the world... That set this landlubber Idaho boy on edge. It didn't matter what swam underneath me, it was going to bite.