instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity

a configuration of marine propellers placed in pods that can be rotated to any horizontal angle (azimuth), making a rudder unnecessary.

a specialized marine propulsion system, highly maneuverable, being able to change the direction of its thrust almost instantaneously, used on tugs and ferries.

a marine system that creates a jet of water for propulsion.

any marine propulsion system that allows a non-nuclear submarine to operate without access to atmospheric oxygen (by surfacing or using a snorkel).