Sand castles are made of tiny grains of sand, formulated into the shape of a castle by frail bonds. To dream of a sand castle means that there may be something in your life such as your career or relationship requiring careful planning before it is built. If you build it too far away from the shore, the transferring of needed water to make the sand castle stay together will be difficult. However, building it too close to the shore and the tide will easily wash it away.
Therefore, you must provide yourself with a sturdy and vigorous foundation before proceeding further ahead. A sand castle in your dream may also be an indicator that you are trying to escape reality and trying to find a place of tranquility.