Possibly in some cases. I suppose it depends on where you were. There was an article in the Washington Post by a reporter who was swimming in the ocean when the Tsunami hit. The only sensation he had was the odd perspective of seeing the coastline going down as the water rose. He was thrown about some but he managed to crawl into an anchored rowboat and survived fine. His wife on shore grabbed a rope tied to a tree and managed to pull herself up and out of the water.
Yes. If you're in deep enough water to begin with, you aren't swamped by a big incoming wave. The guy in question was swimming around some island small enough 1) for a WP reporter to swim around, and 2) for a WP reporter's brother to own. I think he was smart and cool-headed, but also lucky he wasn't in a really wrong situation.