When tasked with defending the world's superpower, it makes sense that the American military is constantly trying to develop and utilize new and better technologies. The Office of Naval Research has recently announced that the Littoral Combat Ship (LCS) Milwaukee is going to be the first of its ships to utilize a new waterjet design, to improve performance and reliability. (Littoral Combat Ships are smaller ships designed to operate near shore.)
For thrust the typical ship uses large propellers, but this technology has many disadvantages such as cavitation. When machinery rotates in water, it is possible for a pressure differential to develop that will generate air bubbles; this is cavitation. Over time these bubbles can cause parts of the metal to wear away, which means it will have to be replaced. Waterjets however are less susceptible to cavitation, which means they will have to be replaced less often. This is due to their smaller design with a nozzle that produces higher static pressure.
The specific design of waterjet to be used on the Milwaukee can move almost a half million gallons of water in a minute, which is more than modern commercial waterjets. When completed, the ship will have four of these, propelling it to speeds above 40 knots (46 mph).
Source: Office of Naval Research