The open hatch of barges is covered by a plastic sheet with plastic piping formed about the edges to receive water for weighting the sheet down on the hatch coaming rim and sealing the sheet in place. The plastic pipes comprise hollow folded over plastic pipes terminating at tapered ends on each side of a rectangular shaped sheet to form filling pipe structure and simple drawstring closure valving to be disposed above water level. Drainage pipes in the barge coaming receive plastic drain sleeves forming passageways from the upper sheet surface to remove any collected rainwater. Plastic air socks located on opposite ends and extending through the sheet permit a blower fan to tent up the sheet in transit for draining rainwater over the edge of the coaming.