Hovercraft are amphibious vehicles that travel on a cushion of pressurised air contained beneath the hull by a flexible skirt, allowing them to operate over water, mud, ice, marsh, sand, and shallow land surfaces without any part of the vessel contacting the surface. Unlike conventional boats, hovercraft generate no underwater drag and are not restricted to navigable water depths.
The ability to cross any flat or gently sloping surface makes hovercraft suited to environments inaccessible to both boats and wheeled vehicles: tidal flats, arctic ice, flooded terrain, and wetlands where draft or ground clearance would prevent conventional access. Military, coast guard, and rescue organisations operate hovercraft for this reason. The type has significant limitations in the private market: noise levels from the lift fans and propulsion propellers are high, the flexible skirt is subject to abrasion and requires regular replacement, and the combination of engineering complexity and specialist maintenance keeps purchase and operating costs substantially above equivalent-performance conventional craft.
Hulls are typically GRP or aluminium, kept as light as possible since total weight directly affects the lift power required. Propulsion and lift are provided by separate or combined fan systems driven by petrol or diesel engines. Steering is achieved through rudder vanes in the propeller airstream; directional control at low speed requires technique different from conventional boat handling. Commercial and military hovercraft range from small two-person craft to vessels exceeding 50 metres capable of carrying vehicles and heavy loads.
