A hydrocopter is an amphibious aircraft-propelled catamaran. The vehicle has a boat-like hull, small wheels and pontoon skids (as in a seaplane). An aircraft engine with aircraft propeller and air rudder pushes the hydrocopter across water, ice, snow and land.
It is very useful in arctic coastal regions during "rasputitsa" or great spring thaw when no boats are usable due to icy seas. It is a cheaper alternative to air-cushion vehicles and helicopters and more suitable in rescue operations during high winds.
see also: Air boat