Training necessities on watercraft have increased during the last few years and real-time simulators offer a suitable and safe alternative. However, the design of a real-time watercraft simulator implies that, water simulation and water-vehicle interaction have to be addressed efficiently. This paper presents a simplified physics model of the water-vehicle interaction for real-time speed-boat simulators that run over 6-DOF motion platforms. The proposed model is highly parametrizable and can be adapted to any speed-boat by changing the values of the parameters. We propose the evaluation of the designed model in a quantitative and a qualitative way. Evaluations results show that the proposed model behaves like a real one in terms of both objective trajectories and subjective perceived experience.