The latest twist to update your propeller. The use of propeller nozzles on commercial vessels is as common as the bulbous bows found on the front of those large ships.
Nozzles are especially successful on vessels that are required to pull and maneuver heavy weights.
It enables tugs to get large barges moving, stopped, and turned. Fishboats are able to pull their nets full of fish through the water and move their heavy cargoes to home port. When an open propeller is spinning some of the water flow is thrown out radially by centrifugal force. Basically a nozzle is a shaped band of steel around the propeller that forces all water coming off the propeller to flow aft. Some nozzles are fixed in place and others turn to perform the function of the rudder as well as directing the flow of water around the propeller.