For generations, fishermen have told tales of sea monsters. One of the world's most legendary monsters is a sea serpent known as Cadborosaurus, or "Caddy," which has been reported off the coast of British Columbia for more than a century. But to science, it doesn't officially exist. Now Pat travels to Vancouver Island to track it down. He questions eyewitnesses, explores the myths of the coastal people who have occupied the area for more than 5,000 years and confers with top oceanographers.