Often referred to as "the unicorn of the sea," the narwhal is guarded by the Marine Mammal Protection Act, according to a release from the U.S. Department of Justice. It's illegal to import narwhal parts into the U.S. or to sell them for anything other than scientific research or uses that enhance the species' survival. Still, the animal's long tusks are commonly collected for display purposes and can fetch large sums of money.