I hit a stump once while perch fishing in a lake during the winter. Fell out of the boat(about 8' deep) with no PFD and was wearing rubber knee boots. I'm a good swimmer, but will never forget that cold water and how my knee boots felt like they were pulling me down as I kicked(tried to swim like normal). Luckily in the heat of the moment I didn't panic, just quit kicking and doggie paddled with my arms to safety. After that day I've had a whole different outlook on wearing knee boots or hip waders in the boat w/o a PFD.