This Sand Hates Water!
If you take regular sand and expose it to trimethylsilanol vapor (ahem, (CH3)3SiOH for the chemists in the crowd), the sand becomes hydrophobic -- literally meaning "water-fearing." The resulting "magic sand" does interesting stuff when exposed to water, as the sand repels the water. Here are two neat videos showing water interacting with water-fearing sand.
Water Drops on Hydrophobic Sand
A weirdly soothing video, this shows what happens as puddles form on top of the sand.
Hydrophobic Sand Underwater
Now things get a little bonkers: pouring the sand into water forms columnar structures (okay, "pooplike" structures) in order to minimize surface area contact of the sand with water. Truly bizarre.