Modern SURREALISM ART GALLERY 2006 by George Grie:

Sand castles are typically made by children, simply for the fun of making them. However, adults sometimes engage in contests making sand sculptures, in which the goal is to create structures which don't appear to be constructed just from sand; they can become large and complex. Other vulnerable media are ice and snow, leading to ice sculptures and snow sculptures. Adults may find sand castle construction to be almost "Zen-like" in its ability to create total focus and relaxation. An example of extremely sophisticated sand art is the Buddhist mandala.