I have had a very close call:

Sailing my Nacra 5.0 with my 11 year old (at the time) in fresh conditions. We were on a screaming reach. I was trapping and he was on the tramp. We stuffed a bow hard, I lost my footing, and I swung forward in front of the front cross beam and got sucked under the boat (or run over)...still hooked on the trap wire. I was being pushed by the water very hard further and further under the tramp, and the trap wire was held extremely tight across the front beam, so tight that it was impossible to unhook myself. Luckily my son understood my screaming and gasping enought to steer the boat into the wind. That slowed the boat enough for my escape.

Although I'm a strong swimmer, I definitely could have drowned that day. I'm looking with interest at the new hook designs coming out. I would much rather risk being separated from my boat (by unhooking) than trapped under it.