Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

In General Efficiency because there is no Hydrodynamics subforum. :)

Submarine Secrets: Pump Jets And Propellers Explained

Complete with helpful diagrams. At the conclusion the future is held to be rim-drive propulsors buried in the hull for stealth. but rim drive thrusters are off the shelf for surface vessels.

edit: Here is an example: https://palanquee.fr/Rim-Drive-Thruster

Quote:

Benefits
■ Unique technology without seals
■ Two solid molded parts - No sealing needed, no oil or air inside
■ High reliability, rugged design
■ Only three moving parts – direct driven propeller – no gear
■ High torque at low RPM
■ Low friction Seawater lubricated bearings – simple to service
■ Hub less propeller - low risk of entanglement
■ Easy exchangeable propeller
■ Symmetrical forward and reverse thrust
...

Specifications
■ Operation depth: 6,000 m
■ Thrust: up to 350 N (35.6 kgf)
■ Power: up to 2,500 W
■ Voltage nom.: up to 110 VDC
■ Max. rpm: 1,400 rpm
■ Weight: 5.6 kg