A Jet ski is a personal watercraft vehicle that can accomodate 1 - 4 persons depending on the model. They were first developed by Yamaha as a one person model, and their popularity has caused other companies to join the booming market for similar watercrafts. The original design had the rider standing or crouching on a small platform towards the rear of the craft. The rider could vary his or her position with a steering column the could move vertically up and down. This aided in variable standing positions as well as letting the rider move with wave action as necessary.

The most notable innovation that came with the Jet Ski design was the jet propulsion system that it incorporated. The Jet Ski was powered bringing water into a tube and pushing out of the rear, thus createing the "jet" effect. This is done by a impeller inside the tube. The tube can also be moved side to side horizontally for steering purposes. This power system is ideal for small watercrafts because it is safe and fast. There is no external propeller or rudder for passengers to worry about. The jet drive is also a very quick means of accelleration for light watercrafts.

Since the first Jet Ski gained huge popularity, the other designs have almost completely replaced the original design. All personal watercrafts still use the same jet propulsion, but the body design is very different. Newer designs are larger and they use a motorcycle style seat that is much more comfortable for cruising and it easily fits more than one passenger. depending on the length of the seat, you can fit 1 - 4 passengers comfortably. The first design of this watercraft was called the WaveRunner and it was made for 2 persons. Modern designs average room for 3 persons because the Jet Ski has now become an alternative to a boat because of its versatility and low price tag.