Which propulsion type includes personal watercraft utilizing a marine jet system?

The propulsion type that includes personal watercraft utilizing a marine jet system is water jet propulsion. This system works by drawing water into a pump through an intake, pressurizing it, and then expelling it through a nozzle to create thrust. This type of propulsion is efficient in shallow waters and allows for quick acceleration, which is ideal for personal watercraft. Water jet systems enhance maneuverability and reduce the risk of damage associated with traditional propellers in shallow environments.

In contrast, the other options represent different methods of propulsion. Propeller systems use rotating blades to create thrust, which can be less effective in shallow water due to the risk of the propeller hitting the bottom. Sail propulsion relies on wind to move the vessel and is not applicable to personal watercraft. Manual propulsion typically involves human effort, such as paddling, which is not relevant to the context of personal watercraft. Thus, the classification of personal watercraft as water jet is accurate and reflects the unique features and advantages of this propulsion type.