We would build them close to the rushing waves, expertly judging the tide. Dig the moat as deep as we could, drop liquid sand pine trees around the base of the hill, run for white sea shells and sand dollars and broken pebbles for doors and windows. You always found a clamshell for the drawbridge and we would raise and lower it until the waves battered our poor defenses with white foam pouring in from all sides and we were helpless with laughter.