Watercraft. This paper presents an experimental characterization of a speed-boat in order to understand the nature and magnitude of a typical small watercraft motion. Unlike other studies, this work focuses on realtime simulation instead of on boat design issues. The purpose of the study is to guide the future process of designing and parameterizing a suitable motion platform for a VR application. The characterization is performed by placing two accelerometers, two gyroscopes, one GPS logger, one digital compass, and one digital anemometer on a speed-boat at several ranges of motion and maneuvering. We analyze tilt, speed, wind, steering, angular speed, acceleration and angular acceleration at both frequency and time domains. Characterization results show that at least a 3-DoF heave-pitch-roll motion platform should be used