An extreme sport (also called action sport and adventure sport) is a popular term for certain activities perceived as having a high level of inherent danger, and that are counter-cultural. These activities often involve speed, height, a high level of physical exertion, and highly specialized gear or spectacular stunts.
In 2004, author Joe Tomlinson classified extreme sports into those that take place in air, land, and water. Nine air sports are mentioned including: BASE jumping, bungee jumping, gliding, hang gliding, high wire, ski jumping, sky diving, sky surfing, and sky flying.
Eighteen land sports including:indoor climbing, adventure racing, aggressive inline skating, BMX, caving, extreme motocross, extreme skiing, freestyle skiing, land and ice yachting, mountain biking, mountain boarding, outdoor climbing, sandboarding, skateboarding, snowboarding, snowmobiling, speed biking, speed skiing, scootering and street luge.
Fifteen water sports including: barefoot water skiing, cliff diving, free-diving, jet skiing, open water swimming, powerboat racing, round the world yacht racing, scuba diving, snorkeling, speed sailing, surfing, wakeboarding, whitewater kayaking, windsurfing.