Nautiluses are relatives of squids and octopuses that are found in warm waters. Unlike them, but like other mollusks such as snails, nautiluses grow a protective shell on the outside of their bodies.
Present-day nautiluses live in waters between 250 and 1,000 feet deep, and swim mainly near the sea bottom. Nautiluses are nocturnal, retreating to deeper water during the day, presumably to avoid predators. The beautiful coiled shell of a nautilus is divided internally into separate airtight compartments. Most are empty, and the animal’s body occupies only the biggest and most recently formed compartment. The empty chambers, mainly filled with air at low pressure, make the nautilus lighter in the water. The animal is not light enough to float, however, and squirts water from