Did you know that tropical sand is made from fish poop?

Pictures and paintings of beautiful tropical beaches usually show gentle blue waves lapping at brilliant white sands. But did you know that much of that sand actually comes from fish poop?

White coral sands are actually made from the remains of coral skeletons. Coral is an animal closely related to anemones and jellyfish, but unlike its squishy cousins, coral polyps join together into groups to form a “skeleton” out of calcium and carbon in the water (calcium is the same mineral human bones are made from). Each coral skeleton can hold thousands of coral polyps, like a giant apartment complex.

Corals form the backbone of coral reefs, which provide homes and food to thousands of species. One such species is the parrotfish. Parrotfish swim through the reefs biting off tiny pieces of coral and digesting the polyps inside. The hard skeleton of the coral can’t be digested by the fish, and instead is ground up by special teeth in the back of the fish’s throat before passing through the fish and eventually forming the beautiful white sands that people flock to on vacation. Parrotfish produce a ton of coral sand for each acre of reef every year!

So remember that every time you see a loving couple walking hand-in-hand down a white tropical beach, they’re actually walking on fish poop! But don’t worry – by the time the sand washes up on the beach, it’s perfectly safe to use for sand castles.