Swash on a plane beach is modelled by using a solution of the shallow-water equations due to Shen & Meyer (1963). The equations are used in a form appropriate for a plane at a finite angle to the horizontal. The beach is cut-off at a level below that of the maximum run-up, and the water is taken to fall freely over the end of the beach. An explicit solution is found which permits evaluation of the overtopping flow and total volume for one swash event.