In stevedoring operations, the ship-to-ship transfer of containers in open-sea is becoming an alternative way to avoid port congestion and subsequently can increase port efficiency. This process involves a large container ship or a barge, equipped with a crane, and a smaller vessel which transports containers between the ship and the harbour. However, the harsh open-sea conditions can produce exogenous disturbances to the crane system during the load transfer. Besides, the uncertainties and disturbances in the crane systemmay degrade the control performance.