A flounder is a fish of the families Achiropsettidae, Pleuronectidae, Paralichthyidae, and Bothidae. Flounders are born with eyes on both sides of their heads, but as they get older, one eye migrates to the other side of the body. This gives them a flattened look, which aids in their concealment on the sea floor. Flounders are found in both fresh and salt water habitats and can grow to be more than three feet long.