right term

A personal water craft (PWC) is a recreational watercraft that the rider sits or stands on, rather than inside of, as in a boat. Models have an inboard engine driving a pump jet that has a screw-shaped impeller to create thrust for propulsion and steering. They are often referred by the names WaveRunner, Jet Ski, or Sea-Doo, which are brand names owned by Yamaha, Kawasaki, and Bombardier, respectively.
Because of their relatively low cost and the freedom they afford to owners, PWC are widely used for recreation. However, many U.S. states require safety training for personal watercraft operators. Modern PWC include a lanyard attached to a dead man's switch, to turn off the vessel if the operator falls off -- provided the lanyard is attached to the operator.
Most are designed for two or three people, though four-passenger models exist. Stand-up PWCs were first to see mass production and are still popular for single riders. The invention of both major types of PWC is usually credited to Clayton Jacobsen II of Arizona, originally a motocross enthusiast.
Lake Havasu, Arizona, is a favorite for PWC riders and racers alike, and hosts the IJSBA World Finals for personal watercraft racing each October since 1982.
Some surfers use PWCs to get to the waves and get up to speed with them; this is known as tow-in surfing. They can also be used for towing water skiers on flat water.
The Ocean Scooter is an inflatable, battery-powered personal water craft with a top speed of only 2.5 miles per hour designed for children ages five

jet engine

A pump-jet or water jet is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle.
Pump jets have some advantages over bare propellers for certain applications, usually related to requirements for high-speed or shallow-draft operations. These include:
Increasing the speed for the onset of cavitation, due to the raised internal dynamic pressure
High power density (with respect to volume) of both the propulsor and the prime mover (since a smaller, higher-speed unit can be used)
Protection of the rotating element and making operation safer around swimmers and aquatic life
Improved shallow-water operations, since only the inlet needs to be submerged
Increased maneuverability, by adding a steerable nozzle to create vectored thrust
Ultra-quiet designs for submarines; for example the Royal Navy Trafalgar-class, the US Navy Seawolf-class, and the French Navy Le Triomphant class. A pumpjet also formed a central plot element in Tom Clancy's novel The Hunt for Red October, although it was changed to a magnetohydrodynamic drive in the film.
Propulsion of torpedoes; for example the Spearfish or Mark 48
In these situations, the benefits outweigh the somewhat reduced efficiency (especially marked at low forward speeds) caused by the increased wetted surface and higher rotational speeds than an open propeller. One disadvantage is that pump jets (especially when fitted to outboard engines) are prone to becoming clogged with debris such as seaweed. The operator must clear the impeller by stopping the craft and briefly revving the engine in reverse.

introduction to machine

Jet-Ski is the brand name of personal watercraft (PWC) manufactured by Kawasaki Heavy Industries, Ltd.. The name, however, has become a genericized trademark for any type of personal watercraft. Jet ski (or jetski, often shortened to "ski"[1]) can also specifically refer to versions of PWCs with pivoting handlepoles known as "stand-ups".
Jetski became foremost the colloquial term for stand-ups because, in 1973, Kawasaki was responsible for a limited production of stand-up models as designed by the recognized inventor of jet skis, Clayton Jacobsen II[citation needed]. In 1976, Kawasaki then began mass production of the JS400-A. JS400s came with 400 cc two-stroke engines and hulls based upon the previous limited release models. It became the harbinger of the success Jet-Skis would see in the market up through the 1990s.
In 1986 Kawasaki broadened the world of Jet Skis by introducing a two person model with lean-in "sport" style handling and a 650cc engine, dubbed the X-2. Then in 1989, they introduced their first two passenger "sit-down" model, the Tandem Sport (TS) with a step-through seating area.
In 2003, Kawasaki celebrated the Jet Ski brand by releasing a special 30th anniversary edition of its current stand-up model, the SX-R, which has seen a revival of interest in stand-up jetskiing. The X-2 has also been updated, based on the SX-R platform and re-released in Japan. Kawasaki continues to produce three models of sit-downs, including many four-stroke models.
The four stroke engines have come on since the late 1990s; with the help of superchargers and the like the engines can output up to 250 horsepower as seen in the newly released Kawasaki ultra 250x.
Since jetskiing has evolved through the 90s other companies like Yamaha, Bombardier and Polaris have joined the sport to make it into a worldwide sport in both racing and freestyle.