An ocean ship which carries barges. These barges are loaded with cargo, often at a variety of locations, towed to the ocean ship, sometimes referred to as the mother ship, and lifted or, in some cases, floated on board. After the ocean crossing, the barges are off-loaded and towed to their various destinations. The ocean ship then receives a further set of barges, which have been assembled in readiness. This concept was designed to eliminate the need for specialized port equipment and to avoid transshipment with its consequent extra cost.