Have spent many a week over the last few years boating the Severn, Thames, Lee, Stort, Wey, Avon, Soar, Trent, Nene and the Great Ouse and its tributaries without feeling the slightest need to wear a lifejacket. If I had been wearing one I would have been about the only person doing so, so there must be an awful lot of total idiots about!
The only time I wear one as a matter of course is when navigating tidal rivers.
Tim