LOL. I suspect he can swim, but doesn't like the water. I had a dog that actually could not swim, if he got out above his height, his butt would go down and he's sink completely, front legs flailing. For some reason, he wouldn't use his back legs, although if you grabbed his tail and brought his rear up, he'd start kicking and do just fine.
So funny! I had a black lab/golden retriever mix that got his collar caught under a dock and almost drown. I had to jump in and rescue him. He was afraid of water after that and my bf had to swim out to retrieve his own ducks! He was great with partridge. Just just don't shoot any birds near water! LOL