Abstract: A concrete breakwater module for use with like modules positioned side-by-side in a line along or offshore from a beach or bluff for preventing erosion due to wave action and for reversing previous erosion. Each module has a single, large, upwardly concave, wave-energy-absorbing trough of partly cylindrical and partly flat-bottomed contour adjacent rear and front upright walls respectively located at opposite ends of a bottom, base wall. The front wall has a sloping front end surface directing incoming waves and spray over the trough. The rear wall is substantially higher than the front wall to intercept waves and spray and re-direct them downwardly along a cylindrical surface and forwardly in the trough providing a rolling and swirling action of water which erupts at the front wall in a countercurrent manner against waves and spray overtopping the front wall.