The determination of the pressures affecting the marine works of a vertical nature is far from being completely understood. The prototype instrumentation and testing of large-scale channels exhibit useful information to define their behaviour at probabilistic level, but not the above methods or existing methods of calculation are capable of responding to complex phenomenon that occurs in wave reflection on the vertical dikes. The results offered are based on very simplified principles and calibrated in accordance with a scale trials, leading to overestimate the works, with the over cost that this entails. In this work we have developed a measurement system that allows a study of the laws of pressures acting on vertical breakwaters, and optimize the design and sizing of the same. This system has been placed in the dock of Botafoc (Ibiza - Spain) and the measured data has led to new results and very revealing as to the form of the distributions of the thrusts, the influence of the wave period on the same, and importance of flows induced by waves through the foundation stools.