Sand and water can be used as two separate activities. Each one on its own provides children with many learning opportunities. As a liquid, water can be splashed, poured, frozen and evaporated. As a solid, sand can be sifted, raked, shoveled and dumped. Play with each substance separately can be used to foster children's socio-emotional, cognitive, and physical growth.
However, when we combine sand and water play the children's experience is enhanced by the creation of a third medium -- wet sand.
Wet sand play allows children to encounter principles of math and science firsthand. When children mix sand with water, they discover that they have changed the properties of both: the dry sand becomes firm and the water is absorbed. The textures of both materials change, too. Unlike dry sand or liquid water, wet sand can be molded. Individually and together, sand and water play can be used effectively to challenge and soothe children's minds and bodies.
P/s:below are 2008's album, enjoy~ >.<
more info :
http://www.littledreamers.com/