[TorpX]

Normally, a moving destroyer that sees a torpedo will put the rudder hard over to turn, and in so doing will slow abruptly, making it look like they are slamming on the brakes. If they are stationary, they will accelerate quickly to get out of the way, and then turn. Obviously, they cannot turn without moving.

I've never seen one back up without reason, but they often will slow to listen, if they are having trouble locating some sneaky submarine.