To capture the combined effects of wind, tides, and waves using real-time hybrid model testing, a system of winches was designed and integrated into the wave tank at the National Renewable Energy Laboratory. These winches provide the additional forces and moments caused by wind, currents, and moorings, which are not physically replicated in the tank. In the initial test of an open-source floating tidal turbine, five servomotor-driven winches apply forces on the device in four degrees of freedom: surge, heave, sway, and pitch. This system will expand the testing capabilities of the wave tank by enabling wind and tidal turbines to be tested, as well as reproducing more realistic loading on all marine energy devices. This paper discusses the motivation and methodology of the hybrid model testing system, in addition to sample results from preliminary testing with the tidal turbine prototype in the wave tank.