both sides initially believed the barrier to be effective and the germans attributed some losses to it. however, in march 1916, the germans found their submarines could traverse the channel on the surface at night. the british moved the barrier to cover folkestone-cap gris nez and used new mines and searchlights, effectively closing the channel to hostile submarines in august 1918. underwater scanning of the area covered by the dover barrage shows the wreck of sm ub-109 broken in half.