Waterski

The butt equivalent of motorboating boobs

All her weight is in the trunk so i went waterskiing

Waterski Racer

Niche group of idiots who enjoy strapping themselves to planks of wood, and hanging on too a piece of rope off the back of a high-end race boat to compete through an imaginary race track made out of floating buoys.

Commonly found repairing not helping their team prepare their boat, putting enough tape on their feet to kidnap a concert, and drinking way too much before they're meant to race.

Evidence : Experience ;)

Bob : "Did you see those Waterski Racers?"
Steve : "fucking idiots! I think they share one braincell."