what animal is called the unicorn of the sea

The animal that is called the "unicorn of the sea" is the narwhal. Narwhals are small, toothed whales found in Arctic coastal waters and rivers. They are famous for their single large tusk, which is actually a protruding canine tooth. The tusk can grow up to 10 feet long and resembles the historical portrayal of a unicorns horn. In medieval times, narwhals were hunted for their tusks, and people would sell them as unicorn horns, earning narwhals the nickname "unicorn of the sea".