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.
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 credited to Clayton Jacobson II of Arizona, originally a motocross enthusiast.
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.
Lifeguards in some areas use PWCs equipped with rescue platforms to rescue water users who get into difficulties and carry them back to shore. Rescuers have also used personal watercraft to pick up flood survivors.
PWCs have been used by biologists studying marine life.
PWCs are also used for law enforcement. Due to their speed and excellent maneuverability, police and rangers use them to enforce laws on lakes and rivers.
A PWC combined with a wash-reduction system, carrying waterproof loudspeaker equipment and GPS for instructions and distance measurement, has purportedly been used by assistant coaches for rowing sports on the River Tyne.
PWC's are used by the US Navy as surface targets. Equipped with GPS, electronic compass, radar reflector, and a radio modem, the PWC is fully remotable with a two way link. Its small shipboard foot print allows it to be stored and deployed from the smallest of vessels and has been used for target practice for everything from 5" to small arms.
Before 1990, personal watercraft emissions were unregulated in the United States. Many were powered by two-stroke cycle engines, which are smaller and lighter than four-stroke cycle engines but much more polluting. Simple two-stroke engines are lubricated on a "total loss" method, mixing lubricating oil with their fuel; they are estimated to exhaust in excess of 25% of their fuel and oil unburned in addition to the products of incomplete and complete combustion.
The 1990 amendments to the Clean Air Act allowed the U.S. Environmental Protection Agency to begin regulating personal watercraft and other off-road internal combustion engines. The agency began a dialog with manufacturers in 1991, resulting in regulations that were enacted in 1996. These regulations, set to phase in between 1998 and 2006, are averaging standards, allowing manufacturers to offset more polluting engines in their range by selling other engines that exceed the standard. The U.S. state of California has adopted more stringent regulations than the federal standard.
To meet these regulations, manufacturers have adopted a variety of improvements, including increased use of four-stroke engines, the use of direct injection for two-strokes and the use of catalytic converters and other pollution-curbing measures that overall have reduced emissions by approximately 75% compared to pre-regulation models.
In some areas, only new personal watercraft that meet the current regulations are permitted; an example is Lake Tahoe.
Environmental groups such as the Surfrider Foundation and the Bluewater Network claim that more rapid progress could be made and the large numbers of older watercraft in use continue to emit substantial pollution.
Against this, industry groups such as the Personal Watercraft Industry Association point out that environmental groups continue to cite pollution levels of pre-regulation watercraft and ignore the improvements made to newer models; and furthermore, that personal watercraft are unfairly singled out when they are no more polluting than other powered boats.
Apart from the obvious hazards of collisions and mechanical breakdowns common to all vehicles, personal watercraft feature the unique hazard of orifice injuries. Such injuries are the logical result of the unusually close proximity of PWC riders to the output end of the pump jet, as well as the fact that personal watercraft are usually not enclosed. A rider who falls (or is ejected) off the back can land directly in the path of the PWC's high-pressure jet of water. Unless a rider is appropriately dressed in garments made out of a strong, thick substance like neoprene (as is commonly found in wetsuits), the jet will easily penetrate any orifice it reaches. The consequences include permanent disability or death. For example, in 2006, the California Court of Appeal (First District) upheld a $3.7 million Napa County jury verdict against Polaris Industries arising out of one such incident (which had devastating effects on the victim's lower abdomen).
PWCs also present safety concerns in terms of their ability to steer. Since steering is achieved from aiming the nozzle of the pump jet, there is no rudder involved, which means the craft cannot be steered in an emergency breakdown situation. Also, steering is significantly reduced when the throttle is not being applied; this leads to dangerous situations because it is against one's instinct in an emergency to accelerate. However, turning is not effective without doing so. After market products are available to help with this problem, including different types of rudder steering systems such as Cobra Jet Steering. In 2001 Sea-doo added the O.P.A.S. (Off-Power Assisted Steering) system which uses rudders installed on the rear sides of the PWC to assist in steering.