There are 840 million acres of public land in the U.S. (over one-third of the country), but the protection of America’s natural wonders extends way beyond just land. There’s water, too, and a lot of it. The Office of National Marine Sanctuaries—kind of like the underwater version of the National Park Service—manages more than 600,000 square miles (384 million acres) of marine and Great Lakes waters. Within that system are 15 designated national marine sanctuaries that hold hidden worlds beneath the surface, from sea spires and coral reefs to shipwrecks and humpback whales. 

In 1972, President Nixon created the National Marine Sanctuary System to secure these underwater historic sites and areas of rich ecological value. Still, many people haven’t heard of these sanctuaries. So, what are they? The special areas are designed to “protect important marine ecosystems around the nation” all while still allowing the public to use the waters as well. Exploring a handful of the most noteworthy National Marine Sanctuaries outlined below will help you better understand and enjoy all that these preserved, protected locations have to offer.   

National Marine Sanctuary of American Samoa

When you think of American Samoa, you should think of coral reefs. Across five islands and two coral atolls are large colonies of Porites coral. And beyond the 250-plus species of coral, its waters boast nearly 1,000 species of fish and 1,400 different types of marine invertebrates like sea urchins and clams. It’s also home to a coral colony—what’s known as Big Momma—that’s over 20 feet tall, 500 years old, and composed of 200 million individual corals. In addition to protecting the coral and other marine life, the sanctuary fosters the culture of the Polynesian Lapita people who reached Samoa over 3,000 years ago. Designated in 1986 and expanded to now protect some 13,581 square miles, the sanctuary also houses the pristine Rose Atoll Marine National Monument, sheltering many threatened and endangered species within its borders. Take advantage of activities to experience the best of the sanctuary, from snorkeling, fishing and diving to island hiking. 

Hawaiian Islands Humpback Whale Marine Sanctuary

This sprawling sanctuary surrounds the main Hawaiian Islands. Its 1,366 square miles protect a nursery that’s crucial for the humpback whale population (Hawaii’s warm water helps the newborns survive), which at one point had been decimated by commercial whaling. Thousands of humpbacks spend winter in the sanctuary waters where they mate and then begin raising their young calves. Visitors enjoy surfing, diving, and snorkeling, as well as observing marine life like seals, turtles and dolphins. November to April is a great time to view the whales from shore or sea. Other U.S. sanctuaries also protect areas where whales return each year, like the Stellwagen Bank National Marine Sanctuary off the coast of Massachusetts, which is an important feeding ground critical for humpback whales. 

Olympic Coast National Marine Sanctuary

This 3,188-square-mile sanctuary, stretching over 135 miles of Washington State’s Pacific coastline, is managed by four tribes—the Hoh, Makah, Quileute, the Quinault Indian Nation—that work closely with the federal government to protect its resources. With waters that are incredibly nutrient-rich and full of sea life, from birds to whales and sea turtles, the shore’s kelp and tidal zones also teem with life. In addition, some 200 shipwrecks have been documented in the area. Visitors enjoy the coastal waters and marine life, often coming to surf, dive, hike, walk the beach, and explore the tidepools. 

Thunder Bay National Marine Sanctuary

Located in Michigan’s Lake Huron is the only freshwater marine sanctuary. Thunder Bay is unique in another way, too: It protects a staggering number of shipwrecks. The 200-plus ships, which in most cases sank as a result of intense storms and collisions, are better preserved by the freshwater. The sanctuary is one of three in the system that protect maritime history (the others are Monitor National Marine Sanctuary, home of the sunken U.S.S. Monitor; and Mallows Bay-Potomac River National Marine Sanctuary on the Maryland side of the Potomac, which is home to over 100 sunken World War I-era wooden steamships). Divers, kayakers, and snorkelers love to explore the wide variety of shipwrecks in the crystal-clear waters (glass-bottom boat tours are available).

Florida Keys National Marine Sanctuary

Home of the third-largest barrier coral reef in the world (the continent’s only barrier coral reef), this sanctuary also has the world’s biggest seagrass bed (habitat for manatees!). Marked by mangrove islands, it protects over 6,000 species of marine life (like sea turtles and herons) and some 400 historic sites (like ships that wrecked at sea during storms and hurricanes). Within its 3,800 square miles are the coral reefs of Tortugas Ecological Reserve. Visitors come to the Keys to dive, swim, snorkel, plus fish for tarpon and bonefish.

All articles are for general informational purposes.  Each individual’s needs, preferences, goals and abilities may vary.  Be sure to obtain all appropriate training, expert supervision and/or medical advice before engaging in strenuous or potentially hazardous activity.