Is it just me or animals never drown when underwater? i also seen them walk on top of water but mostly torpedoing underwater, its so annoying... i havent found a way to stop or prevent this issue... i think its related to pathfinding and navmesh, just my guess.
I've never experienced that kind of bug in vanilla Skyrim, SkyMoMod or Real Wildlife. Usually animals keep away from water and thoose that are able to swim, cross waters without problems. Jesus and torpedo animals on water seems to be exclusive to your mod...

And no, animals do not drown, but they make up easy prey when not able to defend themselfs...
