A jetboat or jet boat is a vessel powered by the emission of a stream of water.
The first successful jetboats were the invention of a New Zealander, Bill Hamilton, inspired by the country's many shallow fast-flowing rivers.
How jet boats work
Jetboat on the Rogue River by Grants Pass, Oregon.
A conventional screw propeller works within the body of water below a boat hull, effectively "screwing" through the water to drive a vessel forward by generating a difference in pressure between the forward and rear surfaces of the propeller blades and by accelerating a mass of water rearward. By contrast a waterjet unit delivers a high pressure "push" out the stern of a vessel by accelerating a volume of water as it passes through a specialised pump mounted above the waterline inside the boat hull.