The flounder is a type of marine flatfish. Flounders lurk on the ocean floor to ambush smaller fish and other prey. When flounders are born, their eyes are located on each side of the head, but as the flounder grows, one of its eyes migrates to the other side so that both eyes are on the same side of its body. As the fish lies on the seafloor, both eyes look upward, alert for prey or predators. To protect itself, the flounder also uses camouflage, changing its color to match its surroundings. For example, the flounder appears a dull, spotted color when lying on the seafloor but turns almost transparent when swimming near the surface. What is the purpose of the underlined sentence?​