Flight Attendants on U.S. airlines spend most of their training on how to deal with emergencies. After all, that's their main job--not serving drinks. They do this training over and over so that in an emergency, they will bark out orders in such a way, no one is going to refuse. It becomes second nature to them.

All of the major airlines have large pools in their FA training centers. Many even have mockups of planes in those rooms.

A flight attendant, as part of training, must be able to don a life vest, inflate a raft, and climb into it while in the water. All unaided.