An air-cushion vehicle (ACV) or hovercraft can travel over land or water supported by a cushion of air ejected downwards against the surface below it. In principle a hovercraft can travel over any sufficiently smooth surface, solid, liquid, mixed, or anything in between. Large hovercraft, riding on an air-cushion contained by skirts several meters tall, can deal with obstacles 1 to 2 meters in height. The smallest personal hovercraft are nimble enough to follow some rolling of the terrain.
One of the benefits of this type of amphibious craft is the possibility of making them large — the British-built SR.N4 Mk.3 ferries could carry dozens of vehicles. ACVs have a high speed over water (an SR.N4 Mk.1 could do 83 knots (95 mph or 154 km/h)) and can make the transition between land and water at speed — unlike most wheeled or tracked amphibians. Drawbacks are high fuel consumption and noise levels.
For some military applications wheeled and tracked amphibious vehicles are slowly being supplanted by air-cushioned landing craft. The hovercraft’s ability to distribute its laden weight evenly across the surface below it makes it well suited to the role of amphibious landing craft. The US Navy LCAC can take troops and materials (if necessary an M1 Abrams tank) from ship to shore and can access more than 70% of the world’s coastline, as opposed to conventional landing craft, that have only about 17% of that coastline available to them for landing.