Floating tidal turbine systems are seen as being preferred to fixed bottom and mid-column systems due to cheaper deployment and maintenance costs. As such, the stability of the floating system under varying flow and surface conditions is as important as the performance of the tidal turbine. The stability of a floating tidal turbine system at various velocities in a tow test was predicted using ProteusDS, and compared against the physical tow test results of the same floating tidal turbine system. The model was calibrated against the static case of the floating tidal turbine system floating in water, and was found to work well with the other cases. The position of the centre of gravity of the platform and the position of the turbine was found to affect the platform stability, with the centre of gravity having a larger influence. The model was also tested under different wave conditions, and an operating envelope was developed. The ability to perform quick and accurate predictions of the stability of the floating tidal turbine system would allow technology developers to optimise the design to fit the site conditions easily, thus saving time and cost.