Marine sanctuaries are protected underwater areas where you can find habitats of species like stony reefs, kelp forests, deep-sea canyons, and even some ancient underwater sites. These underwater preserves act as safe havens for species that are on the verge of extinction or guard historically valuable shipwrecks, just like national parks do on land. The sanctuary sites range from less than one square mile to 139,797 square miles and together form the National Marine Sanctuary System of the USA. Here's a look at five diverse marine sanctuaries in the US where huge humpback whales breed and give birth, temperate reefs thrive, and shipwrecks narrate the tales of a nautical past.