Just in case he finds this thread, the link to Doug Ritter Essentials™ Overwater Aviator Survival Vest™ is there for him to peruse. I consider having flotation/survival gear on person as a requirement for single engine over-water flights. Training in its use and knowing how to swim would be wise too. Looks like he knew how to tread water (check).

BTW, I also like Switlik's Inflatable Single Place Life Raft. In cold northern water it gets a lot of your body out of the water.