In 2003 an accessibility study based on real-time simulations for the S-class container ships of Maersk Sealand was performed at Flanders Hydraulics Research in cooperation with all involved parties (public and port authorities, pilots, tug and shipping company). The regulation for the upstream and downstream navigation on the Western Scheldt did not accept the arrival of a ship with length over all greater than 340 m. The paper describes two main research studies executed to fill in the gap of knowledge about the manoeuvring behaviour of container ships in shallow and confined water: the accessibility of Ultra Large Container Ships with a maximum capacity of 14,000 TEU to the Western Scheldt and the accessibility of the Berendrecht Lock and Delwaide Dock located on the right bank of the port of Antwerp. An integrated simulation platform with mathematical models describing hydrodynamic (manoeuvrability, ship-bank and ship-ship interaction) and external (wind, current, tug assistance) forces and coupled ship manoeuvring simulators helped in evaluating the possibilities and limitations of head-on encounters, lock and turning manoeuvres. The combination of research and training has finally led to the arrival of the MSC Beatrice in April 2009. After a validation period of more than half a year, characterised by a constant adaptation of negotiated restrictions, a new regulation for the upstream and downstream navigation is being prepared.