Abstract: A seawall structure adapted to combat erosion of a shoreline by wave action comprises a perforate wall arranged along and substantially parallel to the shoreline and having openings therethrough facing seaward through which the water of incoming waves may pass. Each opening through the wall forms a tortuous passage for the water so that the energy of the water is dissipated gradually as it flows through the wall, thereby enabling sand entrained in the water to be deposited landward and seaward of the wall, as well as in the openings of the wall. The wall is composed of blocks arranged in horizontal rows and vertical courses, the upper edges of the blocks in the outermost rows projecting above the upper edges of the blocks of the next adjacent rows to provide an interlocking relationship between blocks of the outermost rows and the blocks of the next adjacent rows, as well as to provide for vertical deviations in the openings through the wall.