I think with some people, no matter how clear you make it that something is unsafe or not wise, they will do it anyway. When we lived in Northern Ireland, we visited a local beach onto which you could drive your car. This is fairly common in Ulster. An American serviceman, his wife and small child were driving up and down the beach just above the tide line in a mini. The only other people on the beach were a couple of fishermen, DH, myself and our children. My husband tried to warn the man in the car that the tide was on the turn and he should move his car further up the beach, or off it altogether. He ignored the warning and almost before he knew it, he was in trouble with water washing round the wheels and unable to move. We helped the passengers out of the car and made a futile effort to move the vehicle (getting soaked to the waist in the process) while one of the fishermen went to find a local farmer who had a tractor. By the time the tractor arrived, the car was full of water which was up to the level of the windows. He was shamefaced, his wife was very shaken, and his car was ruined. At least they were safe.