Voith Schneider Propeller
The Voith Schneider Propeller is a specialized marine propulsion system. It is highly maneuverable; being able to change the direction of its thrust almost instantaneously. The system uses a large rotating circular plate, mounted on the bottom of the vessel. The rotating plate has a number of long vertical hydrofoil blades that protrude from it, each of which rotates independently.
The propulsion system alters the direction of the propeller's thrust, and the magnitude of its thrust, by altering the angle of attack of the vertical plates as the horizontal plate they protrude from rotates. This allows instaneous changes of direction simply by altering the blades angle of attack, in a way that is homogolous to how altering the angle of attack of helicopter blades alters the direction of their thrust.
Vessels equipped with Voith Schnieder propellers are not suited for navigating in shallow waters, because the blades protude below the hull.