The dynamic behaviour of an undulating tidal energy converter under wave and current loadings is studied. Therefore, a small scale prototype of a damped pre-stressed undulating membrane is tested in a wave and current recirculatory tank. The membrane’s dynamic profile and hydrodynamic forces are measured synchronously with the surface elevation for both regular and irregular waves in current direction. Spectrum analysis reveals that the response to wave loading depends on the wave frequency and is reduced by damping-type power take-off. Coupling between the wave frequency and the main undulation frequency or its harmonics is also observed. An increase of 30% of the forces must be foreseen in case of wave condition in the tested range.