Extreme sports are about exhilaration, skill and danger.
examples
Surfing
Surfers catch and ride waves.
MTB
Mountain bikes are built to travel at speed over rough ground.
Skateboarding
and more!!!!!!!!!
if you want more information about sports here are some links:
bike, Skating and surfing
http://www.mostvaluabletips.com/sports
http://www.mostvaluabletips.com/sports/wakeboarding
http://www.mostvaluabletips.com/sports/table-tennis
http://www.mostvaluabletips.com/sports/surfing
http://www.mostvaluabletips.com/sports/fantasy-sports
and see this video, for motivation
A good way to get into some of the other extreme sports is to join a club.
That way you can get advice from other people and maybe borrow any special equipment you need.