the sport of snowboarding on mountains or glaciers accessible only by helicopter or skiplane
Big wave surfing is a discipline within surfing in which experienced surfers paddle into or are towed onto waves which are at least 20 feet (6.2 m) high
a form of undersea diving in which the diver enters the water through a hole cut in the ice
BASE jumping is parachuting or wingsuit flying from a building, an antenna, a span, or the Earth (cliff).
