I was doing an "around the boat" once with my brother driving and I came a bit close to a dock. By a bit close I mean I threw myself on my back and slid under the dock, smashing my ski into the pillars. That hurt a bit.
I blame this vid on the driver though, the kid skiing is obviously new to skiing and thus the driver needs to make sure the skier does not hit anything. Slow it up a bit there speed racer.