Narwhal fun facts: Nicknamed the unicorn of the sea, the narwhal's giant horn is actually a big tooth. It can grow up to 10 feet long! Narwhals change color as they age, moving from blue- gray as babies to white when they're old! Dive in! Narwhals are one of the deepest swimmers in the world. 1 in 500 narwhals have 2 giant tusks! Wait - So, I'm not a unicorn? Kellog's Family Rewards: Collect points. Earn rewards. Two easy ways to collect points! Go to KFR.com to learn more.