A busload of beachgoers spills out onto the sand for a day of fun and frolic. Three siblings begin work on a castle, patting and shaping the sand as the sun arcs over the sky. Time and again, their progress is halted: a windswept hat topples their creation; a toddler ambles through it; the tide creeps close, and then too close. Meeting each demolition with fresh determination, the builders outdo themselves time and again, until the moment arrives to pile back into the bus for home