 Marine thrusters come in many different shapes and sizes for example screw propellers, Voith-Schneider propellers, waterjets, ducted propellers, tunnel bow thrusters, and stern thrusters, azimuth thrusters, rim-driven thrusters, ROV and submersible drive units but the thing that ties them all to the same title is their basic function and components.A marine thruster consists of a propeller or an impeller encased in some kind of tunnel that directs the flow of water across the propeller to obtain movement in the desired direction.The two subcategories of marine thrusters are propulsion and maneuvering, the maneuvering thruster typically coming in the form of bow or stern thrusters and propulsion thrusters ranging from Azimuth thrusters to Rim Drive thrusters that have a rotor with propellers facing inwards (Azimuth Thrusters – Kongsberg).