Tracking Narwhals: An Arctic Journey "Nightline" traveled to Baffin Island in the Canadian High Arctic to track narwhals, one of the most elusive creatures on the planet. Known as the unicorn of the ocean, they feature a single tusk that can grow up to 10 feet long. ABC News' Linsey Davis and producer Alex Waterfield endured inhospitable climate and dangerous, cracking sea ice on their journey with Arctic Kingdom Polar Expeditions. Glenn Williams/National Institute of Standards and Technology