The erosion of sand beaches due to oscillatory water particle motion of non-breaking waves can be of importance, particularly where such a beach is fronted by a sea wall supported on spread foundation. Laboratory study was conducted with natural beach sand; waves were generated mechanically. Geometric variables included the inclination of sea walls front 15 to 90 degrees from the horizontal and dynamic variables included ratio of ''lave length to water depth and wave height to water depth. It has been determined that the "ultimate" depth of scour is a function of wave height and that the location of scour is a linear function of wave length.