What are the different types of submarine propellers?

There are two basic types of submarine screws. (Screw is the proper term here as propeller is applied to small craft.) One of the screws is built for silence, and the other is built for speed.

Screws built for speed typically have fewer blades and the blades are wider to grab more water as the screw spins in the water. Screws made for silence typically have narrower, longer blades, and have more of them. This allows them to get more speed with less noise, though not as much speed as a speed screw does.