An estuary is where water from rivers mixes with salt water from the ocean. North Carolina’s Back, Core, and Pamlico Sounds form the country’s second largest estuary, where water, nutrients, marsh grasses, and sunlight create a biological engine that supports plentiful and diverse life. Sheltered by the barrier islands of the Outer Banks, including the islands within Cape Lookout and Cape Hatteras National Seashores, this estuary is rivaled in size only by that of the Chesapeake Bay. Plants and creatures across the food web thrive here, and the rich sea life is an important source of food and income for regional communities. Cordgrass provides food and shelter for birds, crabs, crustaceans, and mollusks. Blue crabs use their sharp claws to tear apart shrimp, worms, and even other crabs. The estuary enclosed by the Outer Banks is a nursery and home to many fish. Tricolored herons feed on crabs, fish, and insects in the muddy waters, and osprey fly over open water searching for fish to eat.