He'd be a fucking killer whale.

From an interview with Mark Z. Danielewski:

You swim on a regular basis – what’s your favorite stroke?
I love butterfly. I love it. It’s exhausting, but there’s something about butterfly that is magical. If you get the rhythm right, the force of the stroke itself hurls you through the water and you have this sense of rising out of the water. So it’s ego and submission and ego and submission. It’s awesome. There’s also an ability to abstract it. With freestyle, you can’t do more than freestyle. But with butterfly, you can imagine that if I had slightly longer legs and a big fin, I’d be flying out of the water. If I could go even faster, I’d be a fucking killer whale.