Jet Ski is the brand name of a personal watercraft manufactured by Kawasaki Heavy Industries. The name is sometimes mistakenly used by those unfamiliar with the personal watercraft industry to refer to any type of personal watercraft; however, the name is a valid trademark registered with the United States Patent and Trademark Office, and in many other countries. The term "Jet Ski" (or JetSki, often shortened to "Ski" is often mis-applied to all personal watercraft with pivoting handlepoles manipulated by a standing rider; these are properly known as "stand-up PWCs." The term is often mistakenly used when referring to WaveRunners, but WaveRunner is actually the name of the Yamaha line of sit-down PWCs, whereas "Jet Ski" refers to the Kawasaki line. Recently, a third type has also appeared, where the driver sits in the seiza position. This type has been pioneered by Silveira Customs with their "Samba".