A jet boat is a boat propel by a jet of water twisted out from the back of the craft. Unlike a powerboat or motorboat that uses a propeller in the water behind the boat; a jet boat draws the water from under the boat into a pump-jet inside the boat, and then expels it through a needle at the stern.
Jet boats were originally designed by Sir William Hamilton (who invented the water jet in 1954) for operation in the fast-flowing and shallow rivers of New Zealand, especially to overcome the problem of propellers striking rocks in such waters, although Italian inventor Second Camping had demonstrated a similar vessel as early as 1931 in Venice.
The difference between Campini's and Hamilton's inventions is that Campini's water jet had a very short lifetime in operation due to some unsolved material problems. Hamilton, unlike Camping, filed for a patent. Jet boats are extremely maneuverable, and many can, from full speed, be upturned and brought to a stop within their own length, in a maneuver known as a Hamilton turn.