I helped with a few salvages over the years, and this involved occasional swims into the cabins of upside down submerged floatplanes. It is very disorienting in there! Ever since, I wear either a life jacket, or floater suit (temperature dependent) while flying at all, over water.
I fly over water a lot, though lakes, so not too far from shore generally. I land on the water a lot. Lots of times, even in the amphibian, an attempt to land on the water would result in a crash (too rough). I'm somewhat afraid of ditching a fixed gear landplane, or any aircraft in rough water. I'm very afraid of being not detectable out there after the plane sinks, and drowning.
In addition to the life jacket, my cell phone is clipped to the life jacket in a water proof bag (available for music players), and I always have a whistle, and some form of signal light. It's the least I can do to prevent being someone's bad statistic.