A jetboat is a boat propelled by a jet of water ejected from the back of the craft. Unlike a powerboat or motorboat that uses an external propeller in the water below or behind the boat, a jetboat draws the water from under the boat through an intake and into a pump-jet inside the boat, before expelling it through a nozzle at the stern. The modern jetboat was developed by New Zealand engineer Sir William Hamilton in the mid-1950s. His goal was a boat to run up the fast-flowing rivers of New Zealand that were too shallow for propellers.