Daniel Vunck, age 7, of Richmond, Va., for his question:

WHAT MAKES SEA WATER LOOK BLUE?

A cup of water is as clear as glass  and sooner or later everybody wonders why an ocean full of water is as blue as the sky. Actually, the shiny surface of the sea acts like a bright mirror. On sunny days it reflects the lovely blue of the sky above. On cloudy days it reflects the grays of the clouds. Sometimes its waters are tinged with multitudes of tiny blue, green or red sea dwellers. In some places shallow sea water is tinted by the sand below.