The Narwhal is a species of whale that is known for its long tusk, which is actually an extended tooth. The tusk is the most prominent feature of the Narwhal and can grow up to 8 feet in length. The tusk is used for sensing and communication, as well as for defense. Narwhals also have a unique coloration, with dark gray or black skin on their backs and white on their bellies. They also have a thick layer of blubber to help them stay warm in cold Arctic waters.