The Romans used to do that to people as a form of capital punishment. Tie 'em in a sack full of cats, toss the sack in a canal. Drowning would kill the prisoner, but they'd be torn up by the panicked cats in the process.
My cat Joaquin can swim. I saw him playing tag with an Iguana and fell in to the pool. He swam to the steps and got out. Shook himself off like a dog. A very proud moment for me