LoL...they are walking deaths. Zombies are already dead. They need no oxygen. So they not afraid of water. Swim? I saw some Zombies in movies, and in games. They are not have any coordinated moves. They are slow. They walk and some time run with their disoriented body parts. But swimming needs some skill full moves. I don't think they can do that. But they may float in water or sink under the water and try to walk there. Even though Zombies are eating brains, they don't have a brain.
There is no uniform code of what zombies can do. Zombies don't exist in real life. They are fictional characters in different horror stories. Whether they can swim depend on the writer of those stories.
If the story writer wants them to be able to swim, they will swim. If he doesn't they won't.
Heh! Assuming zombies are real and is somewhat close to the zombies we see on tv and movies, then NO!
Most if not all TV Series and Movies portray zombies to be brain-dead. They only move to "eat". They lack the capacity to think and move their muscles around like in a swimming position. Swimming needs coordinated muscle movement in order to keep afloat and move forward to which zombies lack.
So yeah! Because zombies are brain dead they lack muscle coordination needed to swim. If I can't even swim then how would zombies do it? XD
I think the conventions of the genre prohibit zombies from swimming. I haven't seen swimming zombies anywhere. I've seen zombies crawl, and walk but never even run. They tend to be very clumsy and stupid and normally only capable of shuffling about aimlessly unless something triggers the desire to eat brains in them. If I saw a zombie swimming skillfully in a movie, I'd laugh. They might be able to walk on the hard bottom of a lake or a river but because they're full of gases from putrefaction, they would float and be carried away streaming water or end up helpless and immobile in still water.
That depends on whether the zombie has taken swimming lessons or not