I have been a river rat all my life. Canoes, kayaks, rafting, and sailing all over the US. On flat water with a stable boat I SOMETIMES go without a my PFD. Any rivers or white water or when sailing-I ALWAYS wear my life jacket. I have saved several people on the water when I saw them having trouble. I pulled my god-daughter's mother out of whitewater because according to her, she had been swimming her whole life. It is very difficult to swim if you are knocked out, which can happen easily in whitewater or a sailboat boom hits you upside the head.
Enough preaching, this is an RV site.