I'm a cat person. I'd save my cat. The hypothetical child should know how to swim, like that one kid in "Captain America: The First Avenger" that was thrown into the harbour by a Hydra agent, but told Steve Rogers to go after the Hydra agent because he could swim. If the hypothetical child doesn't know how to swim, that's not my fault. I'd toss him a safety tube and wish him luck as I save my cat.
...Vin