There is a bug where canibals drown themselves in bodies of water like a lake or river.
#Drowning canibals
spring sinew
cursive nest
I don't think that's a bug. Even in The Forest cannibals and mutants can't swim and will drown if they end up in water too deep to stand/run in. Sometimes the AI makes them do stupid things and they commit suicide without your help but I also use it to my advantage when fighting groups of them standing in the water with my back too the deeper water so they can't ambush me from behind. You can also dodge them if they jump at you and make them land in the deep and drown.