A narwhal is like the unicorn of whales, with a long pointy tusk sticking out of its head. And, like unicorns, you probably won't spot one (unless you are traveling the Arctic waters near Greenland).
Only male narwhals have a distinctive ivory tusk, which is actually a long, protruding canine tooth. It's a medium-sized whale, related to the beluga, and it's able to dive underwater for up to 25 minutes at a time. Narwhal comes from the Danish narhval, with the Old Norse root nahvalr literally meaning "corpse whale," for the narwhal's pale white color, thought to resemble the shade of a dead body.