Shore protection by small seabed bars was once considered possible because seafloor undulations strongly reflect surface waves of twice the wavelength by the so-called Bragg resonance mechanism. The idea, however, proved “unreliable” when Yu & Mei (J. Fluid Mech., vol. 404, 2000, pp. 251-268) showed that a patch of longshore seabed bars adjacent to a reflective shore could result in larger wave...