BASE jumping is parachuting or wingsuit flying from a building, an antenna, a span, or the Earth (cliff).
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
the sport of snowboarding on mountains or glaciers accessible only by helicopter or skiplane
a form of undersea diving in which the diver enters the water through a hole cut in the ice
