Container ship at sea. The containers, stacked on the deck of the ship, are used to package and transport cargo, and are lifted on and off the ship by the crane (white, upper centre, partially seen). This container ship, the Ruoon, has just left Antwerp Harbour, on the Westerscheld Estuary, in the Netherlands. Like much of the world's merchant shipping, this container ship is registered under a flag of convenience. In this case, as seen at lower left, the ship's registered port is Monrovia, Liberia.