What is so special about submarine propellers? It's really pretty simple when you are lucky enough to have the world's foremost experts explain it in simple terms, and you don't need to be familiar with "tip vortex flowfields." As props turn, the angle of the blade pushes through the water, driving the submarine. Once they reach a certain speed, the blades begin to create a partial vacuum, which results in air bubbles. This is a state known as cavitation. Bubbles are noisy, and submarine propellers are designed and shaped to reduce cavitation and exploit other relevant laws of physics as much as possible and still maintain useful speeds. Of course, balancing all of these factors results in a compromise, and our newest generation of submarines, the Seawolf-class, does not even use propellers. Neither will the future generation, the Virginia-class, still on the computer design screen. Other options offer fewer disadvantages.