Sperm Whales are best known for their diving abilities. How do they manage to move their heavy bodies deep underwater -- and then have the energy to get back to the surface for another breath? The Sperm Whale’s square, bulbous head is filled with an oily substance called spermaceti, which is believed to control the whale’s buoyancy, or ability to float. When a Sperm Whale wants to dive, it cools the oil into a waxy substance, making itself heavier; when it wants to come back to the surface, it pumps blood around the spermaceti, heating it up and making itself more buoyant.
