A sand castle that was changed by the ocean waves would be slowly taken away from by the waves and would just become a smooth mound of sand. If Dylan stomped on it then it would still have all of the same sand as before but in a different shape. It would also become a mound of sand but it would have all the same sand as before.
(I don't know if I was supposed to talk about fancy physics stuff so I just gave a basic explanation. I don't know if my answer is really right or not... hope it helped though :))