Countershading is a form of camouflage in which the top of an animal’s body is darker in color, while its underside is lighter. Sharks use countershading. When seen from above, they blend in with the darker ocean water below. This makes it difficult for fishermen—and swimmers—to see them. When seen from below, they blend in with lighter surface water. This helps them hunt because prey species below may not see a shark until it’s too late.