Forever associated with Melville's classic Moby Dick, sperm whales are mysterious deep-sea diving creatures who can hold their breath underwater for more than an hour at a time. Author Alison Imbriaco describes how these mammoth cetaceans, known as the most social and loyal of the whales, communicate and hunt for prey using a special sense called echolocation. She details the threats endangering them, including ocean and noise pollution, entanglements in fishing nets, and global warming, and describes what you can do in your daily life to help reduce these threats.