During the design work on a new port on the Colombian west coast the contractor, Armerad Betong Vagforbattringar AB, Sweden, decided to have the possibilities of entering and departing from the future port with different types of ships investigated. The port at Bahia de Malaga, will be exposed to considerable tidal current and, as for the approach fairway, to some extent also to waves of long periods ("swell"). The study was carried out in the SSPA Manoeuvering Simulator, which consists of a simple presentation of the surroundings and of all the vital instrumentation that is to be found on the real ship. The ships investigated are represented in the simulator by mathematical models of the ship dynamics. The input in these models is principally the rudder angle and the engine setting, physically controlled by the rudder wheel and the engine telegraph. The motion of the ship is presented to the "operator" in the form of a bird's eye view of the ship, buoys, lighthouses and surrounding land contours and of a small sector of the front view. The paper gives the background to the project. All the mathematical models, of ship and tug dynamics, wind, current and wave influence on the ship's as well as the tug's behaviour will be all the results gained from the study.