Azimuth thruster

An Azimuth thruster is a configuration of ship propellers placed in pods that can be rotated in any horizontal direction. A conventional rudder is not needed. These give ships better maneuverability than a fixed propeller and rudder system. Primary advantages are electrical efficiency, better use of ship space, and lower maintenance costs. Ships with azimuth thrusters do not need tugs to dock, though they still require tugs to maneuver in difficult places.
See more at Wikipedia.org...