The act of frolicking around at any waterpark in particular and 'accidentally' manuvering your toe into the crotch of a nearby, and conveniently located fellow park guest. Best performed in a large wavepool or other deeper, agitated water attraction where there is a sizeable group of people in close proximity to one another and limited chance of being immediately discovered as the perpetrator of the act. Usually done in order to satisfy one's urges to make physical contact with a hot, young chick in a way that my wife won't notice.
It happens in the middle of the night when you wake up with a massive dookie pain, rush to the bathroom and don't notice the toilet seat is up. A bare butt hitting cold water at 2am usually causes the person to yelp loud enough to wake everybody in the house.
Julie: "Eeeee-ahhhh!"
Kelly: "What happened in there?"
Julie: "You left the freakin'toilet seat up again! I had a splashdown!"
Kelly: "I bet you're awake now."