An employee was descending the side of a barge, having ascended to the top of it to close an opening on top of the barge lid. There was a towing rope on top of the three-step ladder on the barge; the employee put his weight on this rope, believing it to be part of the ladder, and fell backward. His ankle and shin were caught between the top of the third step and the barge lid. He suffered a fracture near the right ankle and another near his right shin and was hospitalized, undergoing surgery.