The sport of sledging combined with that of kayaking. usually done by students in winter when the rivers are either frozen or too cold to paddle. Involves sliding down a hill in a kayak using your paddle to steer the kayak away from obstacles such as trees and small children
Adding unnecessary style flurishes to skilled activities, often beyond ones skill level, increasing the risk, and usually used to taunt or impress others.
That skateboarder was showboating to impress that girl when he broke his ankle.