S1, E1: America's newest marine sanctuary, Papahanaumokuakea Marine National Monument, encompasses the Northwestern Hawaiian Islands. The monument is bigger than all U.S. national parks combined-- yet the majority of this environment has never been seen. What is in this vast marine conservation area? And, what will it take to protect it? National Geographic embarks on a month-long expedition to explore stunning coral reefs, shallow water environments, and rare species unique only to Hidden Hawaii.