A ducted propeller, also known as a Kort nozzle, is a marine propeller shrouded with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily load
Kort nozzle
The towboat Dolphin I in a floating drydock on the Mississippi River, in Algiers, Louisiana
Azipod is a trademarked azimuth thruster pod design, a marine propulsion unit consisting of a fixed pitch propeller mounted on a steerable gondola containing the electric motor driving the propeller,
Ducted propeller
…duct. This type is used for high speed vessels with increased exposure to cavitation and vessels that want to reduce noise levels, such as warships. Azipod – Electric drive azimuth thruster Axial fan design – Fan that induces gas flow mostly parallel to the shaft…
Closeup of one of USCGC Mackinaw's 3.3 MW Azipod units
The first Azipod unit, installed on the Finnish fairway support vessel Seili in 1990, is displayed at the Forum Marinum maritime museum in Turku, Finland.