A hovercraft--moves easily because it has less friction

A hovercraft is an amphibious vehicle that is supported by a cushion of slightly pressurized air and moves just above the surface, be it land or water. The compressed air serves as a cushion that eliminates almost all friction between the vehicle and the surface. Although often seen as a mysterious, even bizarre mode of transportation, it is conceptually quite simple.

To understand how hovercraft work, it is necessary to realize that the dynamics are more closely related to aircraft than to boats or automobiles. As a member of a family of air cushion vehicles (ACVs) or Ground Affect machines, which includes wing-in-ground-effect or ram wings, surface effect ships, sidewall hovercraft, and surface skimmers, hovercraft, are the amphibious members of the air cushion vehicle family. They are the most novel among vehicles that are supported by pressurized air. Refer to the illustration below as you read about exactly how hovercraft work.

Hovercraft float on a cushion of air that has been forced under the craft by a fan. This causes the craft to rise or lift. The amount of lift can range from 6" to 108" (152mm to 2,743mm) depending on the size of the hovercraft. The amount of total weight that a hovercraft can raise is equal to cushion pressure multiplied by the area of the hovercraft. To make the craft function more efficiently, it is necessary to limit the cushion air from escaping, so the air is contained by the use of what is called a hovercraft skirt. Fashioned from fabric, which allows a deep cushion or clearance of obstacles, hovercraft skirts vary in style ranging from bags to cells (jupes) to separate fingered sections called segments.

Once "lifted" or "on cushion", thrust must be created to move the hovercraft forward. With many craft, this is generated by a separate engine from the one used to create the lift, but with some, the same engine is used for both. As the diagram above indicates, the fan-generated air stream is split so that part of the air is directed under the hull for lift, while most of it is used for thrust.

Now that the hovercraft has lift and thrust, it must be steered safely. This is achieved through the use of a system of rudders behind the fan, controlled by handlebars up front. Steering can also be controlled by the use of body weight displacement ... a skill which is achieved after practice.

Source:http://www.discoverhover.org/abouthovercraft/works.htm