A flatfish is a type of ocean fish with a remarkable and unusual body: it's extremely flat and thin, like a pancake swimming sideways along the seafloor. Flatfish include flounder, halibut, and sole.

What makes flatfish truly extraordinary is that they're born looking like normal fish, swimming upright with an eye on each side of their head. But as they grow, something astonishing happens: their body flattens and one eye migrates across their skull to join the other eye. The adult flatfish then spends its life lying on its side on the ocean bottom, with both eyes looking upward. The top side develops colors and patterns to match the sand or rocks, while the bottom side stays pale.

This transformation isn't a defect but an adaptation. By lying flat against the seafloor and matching its surroundings, a flatfish becomes nearly invisible to both predators swimming above and to the small fish and crustaceans it hunts. Some flatfish can even change their color and pattern to match different ocean floors, like a living camouflage costume. When prey swims close, the flatfish explodes upward in a burst of speed to catch it.