It's hydrophobic sand. Water-abhorring sand. H2-Ohhh-Nooo! sand. That's not to say it never learned to swim because its mama spent its swim lessons money on black market Ritalin, just that it physically repels water. It never really gets wet. Dyed in neon colors, the resultant loping and lolling of Magic Sand through a clear container produces a swell effect for kids and bored grownups to play with and stare at.
Presumably, Magic Sand has been treated with a substance similar to Liquipel or NeverWet, which can also waterproof stuff like your smartphone and the spankin' new white Keds you just got from 1986. Visually, the repellent behaves like oil, refusing to intermix with the likes of water molecules. Unlike oil, Magic Sand sinks. Also unlike oil, Magic sand is--and remains--completely dry. So once the novelty of swirling pink and purple and blue and green together through a glass bowl to make unicorn pee wears off, you need only grab a spoon and scoop the sand back into its pouch, mess-free unless you've got a tremor it or sneeze on it.
Magic Sand comes in 1-pound packages.