Succussive layers of sand accrete on the beach as waves bring it up. It is unclear to me whether each wave actually brings an entire horizontal layer of sand a few grains thick or whether it just brings and leaves a line of sand a few grains thick right at the upper edge of the wave. I think it is the former, but my experiments to prove that have gone awry [e.g. put a wet piece of paper down on the sand and see how much sand stays on top after the next wave].