I know about the swimming being extremely dangerous, so i advised my girlfriend who just began playing to not buy it.
well, she was foraging and hunting rabbits a bit, and leftclicked at a paved tile, just in the vicinity of a river. at that exact moment, the server had a major lag, like 2 minutes or so. i think it didn't crash, and she kept walking in the same direction, walking over the water etc. she was forced out of the game(logged out). trying to login she saw that her character was dead.
presumably drowned, there was no evidence of other trauma or possiblities.
so, i think this is a somewhat harsh bug.