I've had a lot of snakes drown their food. Mostly the speckled racers I had. They'd grab the rat pinkies, drag them all the way to the bowl, and hold them in until they died. Only seen a few BPs do that, though, and they'd usually just leave the body in the bowl afterwards.

I've also had f/t eaters do the same thing regarding not constricting. My first BP ate f/t (and I did not know that until later on), and she swallowed the rat alive. Odd thing was the rat didn't even put up a fight. It just sat there all the way down.