The sperm whale is the deepest diver of the great whales and can descend to depths of over 3,300 feet (1000 m) and stay submerged for over an hour. Average dives are 20-50 minutes long to a depth of 980-1,970 feet (300-600 m). At such great depths there is little or no solar light. However, organisms at these depths may produce biochemical light (bioluminescence). Sperm whales use their highly developed echolocation ability to locate food and to navigate, making nearly constant clicking sounds that pulse through the water. Sperm whales communicate using "morse-code" like patterns of clicks called codas. There is also a theory that sperm whales may stun their prey with a burst of sound.The sperm whale's head houses a large reservoir containing spermaceti, a clear liquid oil that hardens to a waxlike consistency when cold, and has long been prized by whalers. Ambergris, a strange substance found in large lumps in the lower intestine of sperm whales, is formed around squid beaks that remain in the stomach. It was used in the making of perfume, and continues to be valuable in spite of its widespread replacement by synthetics.