Magic Sand begins as normal looking sand, until it's dyed and coated with a substance that repels water. This coating keeps the sand dry even after it has been dumped into a container of water. The substance is a regular sand that has been coated with an oil-like substance that is water-hating or hydrophobic. Hydrophobic substances do not mix with water. The term “water-fearing” is often used to describe the word hydrophobic.