Marine thruster

A marine thruster consists of a propeller or impeller which may be encased in some kind of tunnel or ducting that directs the flow of water to produce a resultant force intended to obtain movement in the desired direction or resist forces which would cause unwanted movement.

Their purpose is to maneuver or position the boat to a greater precision than the propulsion device can accomplish.

Another smaller subset of positioning thrusters is those used for maneuvering unmanned aquatic vehicles like Guanay II AUV tested by scientists from Spain (Masmitja, 2018).

Propellers are designed to work in-line with a propulsion plant and produce one-directional thrust while thrusters are more customizable and have a more versatile application.

They have this versatility at the cost of complexity and lower efficiency – they are not as robust as propellers and typically have applications on smaller vessels that don't require as much power.