A friend of mine had just bought his first boat, a 25-foot cruiser, and kept it in dry storage at a lake. He and his wife launched it for the second time, had a nice sail, and then pulled it out of the water for the recovery. Before the original launch, his wife, not knowing better, had unlatched the clamp on the trailer ball, as well as the safety chaines, at the same time she had disconnected the lights from the trailer to the car. So the trailer hitch was sitting loosely on the ball. My friend then continued up the road to the dry storage area. About halfway there, the road took a sharp left turn and went up a steep hill. He made the turn and started up the hill. Behind and below him was a parking lot, and below that was the rocky shore of the lake. Suddenly he noticed that the boat was getting smaller in the rear view mirror. Horrified, he turned and watched the boat and trailer glide back down the road, through the parking lot (missing every car there), and on to the rocky shore, where it came to rest just short of the water. The boat had no damage! The boat had traveled about 100 yards on its own. (For those who know the area, this happened at the Lake Clinton Marina in Lawrence, Kansas.)