This is a way of stopping a ship or turning a ship with a tractor tug. If you stay right behind the ship you will slow/stop a ship. If you were to get on the quarter of the ship you woud slow it down & turn all at the same time. This particular tug is a Voith Schneider equipped propulsion. You can do the same with a z-drive tractor tug. A conventional tug would flip over. They are a fun maneuver. I have done it with a Voith & a Z-Drive tractor tug...AWESOME simply AWESOME!