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") originally referred to personal watercraft with pivoting handlepoles manipulated by a standing rider; these are now known as "stand-up PWCs." Today the term is often 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".