noun - Jet Ski is the brand name of a Personal water craft 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 units are often used for safety purposes in open water swims.
The term "Jet Ski" (or JetSki) is often misapplied to all personal watercraft with pivoting handle poles 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.
These kinds of watercraft are used by lifeguards to make rescues in the ocean.