This paper shows the design of a neuro-fuzzy system to control the vertical motion of a TF-120 fast ferry, so that to improve the comfort of the passengers by reducing the main cause of the seasickness. The aim of this controller is to decrease the pitch acceleration by controlling the position of some actuators, varying their working angles. The controller is based on a fuzzy model of the ship behaviour. It has been simulation tested in regular and irregular waves with satisfactory results. An index, the MSI (Motion Sickness Incidence), has been evaluated to prove the efficiency of this strategy. Although neuro-fuzzy controllers have been widely used before, the application of this strategy to control marine systems is novel.