personal watercraft (PWC), a lightweight vessel usually less than 16 ft (5 m) long that uses an inboard water jet pump, powered by an internal-combustion engine, as its primary source of propulsion. The PWC is operated by a person or persons sitting, standing, or kneeling on it, rather than inside it, as in a conventional boat. The PWC concept originated in the 1960s when a home inventor built a powered water ski that combined the elements of self-power, small size, and a maneuverable, active ride that are distinguishing characteristics of all personal watercraft. The first commercial craft, a sit-down-style PWC, was introduced in the late 1960s, but the PWC did not become commercially successful until the 1970s. Multiperson craft, carrying two, three, or four persons, are now the most common PWCs. Personal watercraft have been criticized for producing noise and air pollution, and tend more than other vessels to be maneuvered in ways that endanger the safety of other boaters. Improved engine designs, increased hull insulation, and water-safety education requirements have resulted in reduced pollution and safety improvements.