(Material aspects)

Sand can represent impermanence. Because they will inevitably be washed away by the tide, building sand castles in dreams suggests that there is some doubt about the validity of a project in which we are involved.

They also indicate that the structure we are trying to give to our lives does not necessarily have permanence and may be an illusion. You might also like to consult the entries for beach, digging / excavation, hourglass and time.