The 'gnarliest' form of kayak bravery tackling hard grade 5 rivers and high waterfalls.
Extreme, in the broadest term, includes a multitude of classes that mere mortals would not attempt with a barge pole: lofty waterfall-running; 'creeking' where paddlers descend steep and low-volume flows; dam-running; extreme river wave surfing; and of course extreme-racing against the clock.
Then there is 'free-boating', otherwise known as 'freeride kayaking' or 'downriver freestyle', this is the extreme sister of freestyle; a fusion of creeking and playboating - paddlers attempt tricks over waterfall lips or in grade 5 rapids.
There are several international and open events that are held each year which are privately organised, the blue-ribbon competition of the calender is the Adidas Sickline Extreme Kayak World Championship in Ötztal, Austria.
Adidas Sickline: http://www.adidas-sickline.com/
Whitewater Grand Prix: http://www.whitewatergrandprix.com/
Go Pro Mountain Games (kayaking: creeking, freestyle, 8-ball sprint, downriver; rafting: raft cross, downriver sprint): http://www.mountaingames.com/summer
Red Bull Dolomitenmann (kayaking, trail-running, mountain biking): http://redbulldolomitenmann.com/