The vertical dimensions in manoeuvring areas can be precisely calculated using probabilistic design, considering the main variables in detail, beyond the general deterministic formula: vessel type and size, access draughts, tidal level and depth, course and speed (squat), direction-period-wave height. In this way, access draughts to the Exterior Port at A Coruña (Spain), the ports of Jorf Lasfar and Safi (Morocco), the port of Buenaventura (Colombia) and the port of Quequén (Argentina) have been improved.