You are assuming too close an association between time and efficiency. Changes of transport mode tend to be personnel and equipment expensive. Likely it would be cheaper and more efficient to not change mode and just have the ship wait for some period. In the transport industry there is an oft quoted allegation that it is cheaper to load a ship at Long Beach, sail it around the world and discharge it back at Long Beach than it is to load the ship, leave Port, immediately return, discharge and repeat.