Mallows Bay on the tidal Potomac River in Maryland is home to nearly 200 known shipwrecks spanning from the Revolutionary War through the present, and including the remains of the largest “Ghost Fleet” of World War I wooden steamships built for the U.S. Emergency Fleet, which are listed on the National Register of Historic Places. Mallows Bay is a largely undeveloped landscape and waterscape identified as one of the most ecologically valuable in Maryland, as the ship remains provide important habitat for fish and wildlife, including rare, threatened and endangered species.

Wisconsin – Lake Michigan is an 875 square mile area of Lake Michigan with waters extending from Port Washington to Two Rivers. The state of Wisconsin nominated this area as a national marine sanctuary through the Sanctuary Nomination Process with broad community support. The area encompasses historic shipwrecks of national significance that merit the additional management authority of the National Marine Sanctuaries Act. The nominated area contains an extraordinary collection of 39 known shipwrecks, 15 of which are listed on the National Register of Historic Places.

Papahānaumokuākea Marine National Monument (PMNM) is the largest conservation area in the world, protecting over 580,000 square miles of Pacific Ocean. The extensive coral reefs found in Papahānaumokuākea – truly the rainforests of the sea – are home to over 7,000 marine species, one-quarter of which is found only in the Hawaiian Archipelago. Many of the islands and shallow-water environments are important habitats for rare species such as the threatened green turtle and the endangered Hawaiian monk seal. On less than six square miles of land, over 14 million seabirds representing 22 species breed and nest. Land areas also provide a home for four species of bird found nowhere else in the world, including the world's most endangered duck, the Laysan duck.

Hawaiian Islands Humpback Whale National Marine Sanctuary is a vital component for the protection of the Humpback whale population, as it is the only place in the U.S. where Humpback whales reproduce. Scientists estimate that two-thirds (approximately 10,000 whales) of the entire North Pacific humpback whale population migrates to Hawaiian waters to breed, calve and nurse their young. No one knows exactly when humpback whales first began wintering in the warm, shallow waters around the Hawaiian Islands. Narrative reports from whalers document the appearance of these majestic giants in Hawaii in the 1840s, but little evidence substantiates an earlier presence. In addition to the magnificent whale watching opportunities, the Hawaiian Islands Humpback Whale National Marine Sanctuary also provides opportunities for surfing, diving and snorkeling.

The National Marine Sanctuary of American Samoa supports one of the most diverse ecosystems in the National Marine Sanctuary System. Some of the marine life that finds a home in the sanctuary includes invertebrates, fishes, turtles, marine mammals and marine plants. The sanctuary protects extensive coral reefs, including some of the oldest and largest Porites coral heads in the world, along with deep water reefs, hydrothermal vent communities and rare marine archaeological resources. Located in the remote islands of Polynesia, it is also the only true tropical reef within the National Marine Sanctuary System. It encompasses 13,581 square miles around the culture-rich islands of American Samoa. Visitors to the sanctuary can enjoy recreational activities such as diving, snorkeling and fishing as well as experience the cultural heritage of the islands.

Olympic Coast National Marine Sanctuary includes the longest stretch of wilderness coast in the lower 48 United States and is unmatched in pristine nature, timeless landscapes, and sublime serenity. The sanctuary protects a productive upwelling zone, home to dozens of marine mammals and seabirds. Along its shores are thriving kelp and intertidal communities, teeming with fishes and other sea life. Communities of deep sea coral and sponges scatter the dark seafloor and form habitats for fish and other important marine wildlife. Sharing the 135 miles of coastline with Washington Coastal Treaty Tribes, Olympic National Park, and Washington State Parks, the sanctuary offers visitors a wide variety of activities ranging from cultural enrichment to ecosystem exploration.

Greater Farallones National Marine Sanctuary (GFNMS) is a globally significant and extraordinarily diverse marine ecosystem that supports abundant wildlife and valuable fisheries. In 2015, GFNMS expanded north and west of their original boundaries to encompass 3,295 square miles. The Farallon Islands, located in the south-central part of the sanctuary, are a national wildlife refuge, offering resting and breeding sites for marine mammals and seabirds. The sanctuary has thousands of seals and sea lions, and is home to the largest concentration of breeding seabirds in the continental United States. Visitors to GFNMS can enjoy activities such as camping, tidepooling and surfing.

Cordell Bank National Marine Sanctuary (CBNMS) is a lush feeding ground for many marine mammals and seabirds. During the spring and early summer, a process called upwelling brings cold, nutrient-rich water towards the surface – causing an explosion of biological activity. Algae and invertebrates thrive in the nutrient-rich water, which attracts a vast array of fish and marine mammals for feeding. Humpback whales, Pacific white-sided dolphins, Dall's porpoises and California sea lions can be seen throughout the summer and fall. However, few people have seen this special part of the California coast due to its depth, currents and distance from the mainland. Visitors to CBNMS should check the events calendar for boat tours on the sanctuary waters.

Monterey Bay National Marine Sanctuary (MBNMS), located in the Pacific Ocean off the central California coast, was designated and protected as a national marine sanctuary in 1992. This vast area stretches almost 300 miles north to south, extends an average of 35 miles offshore, and encompasses over 6,090 square miles. The sanctuary is managed to balance recreational and commercial uses with protection of natural resources, water quality, habitats and its bountiful resident and migratory marine life. In the southern half, visitors will find a mostly undeveloped shoreline of rocky cliffs and steep mountainsides. The northern shoreline is similar but is dotted with settlements of small towns and moderate-size cities. Visitors to MBNMS can enjoy surfing, diving, snorkeling, tidepooling and camping. Additionally, visitors can view the stunning coastline without getting wet by hiking, biking and touring by car.

The waters that swirl around the five islands within the Channel Islands National Marine Sanctuary combine warm and cool currents to create an exceptional breeding ground for many species of plants and animals. Forests of giant kelp are home to numerous populations of fish and invertebrates. Every year, over 27 species of whales and dolphins visit or inhabit the sanctuary including the rare Blue, Humpback and Sei whales. On the islands, seabird colonies and sea lions flourish, while overhead Brown pelicans and Western gulls search the water for food. The Channel Islands National Marine Sanctuary is located 25 miles (22 nautical miles) off the coast of Santa Barbara, California. Visitors to the Channel Islands National Marine Sanctuary can enjoy recreational opportunities such as tidepooling, diving, snorkeling and kayaking.

Thunder Bay National Marine Sanctuary (TBNMS) is located in the Great Lakes water off the coast of Alpena, Michigan. Lake Huron's unpredictable weather – murky fog banks and sudden gales – coupled with rocky shoals helped Thunder Bay earn the unfortunate name of "Shipwreck Alley." During the Great Lakes' 200-year shipping history, scores of vessels ended their careers on the lake floor in the area. However, the known wrecks are only a small section of the total wreckages that have occurred; many wrecks remain undiscovered. These vessels, preserved in time within the fresh, cold waters of Lake Huron, still have stories to tell of Great Lakes maritime history and commerce, from the earliest explorations to westward expansion in the 1800s and modern day lake trade. Through exploration, education and research, TBNMS preserves the lore of Great Lakes maritime heritage.

Stellwagen Bank National Marine Sanctuary (SBNMS) is located at the mouth of Massachusetts Bay. The sand and gravel plateau that gives the sanctuary its name was formed by the slow retreat of massive Ice Age glaciers, which sculpted the dynamic seafloor. The nutrient-rich waters above and around the bank support a diverse ecosystem that has been a famous fishing ground for more than 400 years and claims status as the birthplace of East Coast whale watching. Historic New England shipping routes cross the sanctuary, and over the course of centuries, the seafloor has become a repository for shipwrecks – time capsules of our maritime heritage. The entire sanctuary encompasses 842 square miles of open ocean 25 miles east of Boston. Visitors to SBNMS can enjoy whale watching, bird watching, diving and fishing in this history-rich and biologically-diverse habitat.

Monitor National Marine Sanctuary (MNMS) was designated as the nation's first national marine sanctuary on Jan. 30, 1975. The site was named after the wreck of the USS Monitor, a Civil War vessel that lay deep beneath the ocean surface off the coast of North Carolina. The Monitor was the prototype for a class of U.S. Civil War ironclad, turreted warships that significantly altered both naval technology and marine architecture in the nineteenth century. Designed by the Swedish engineer John Ericsson, the vessel contained all of the emerging innovations that revolutionized warfare at sea. Through a combination of education, archaeology, marine science and regulatory programs, MNMS staff conserves and preserves the rich maritime heritage of the Outer Banks of North Carolina and the “Graveyard of the Atlantic.” Visitors to MNMS can enjoy the many attractions of the Mariners Museum, located in Newport News, Virginia.

Gray's Reef National Marine Sanctuary (GRNMS) comprises one of the largest near-shore sandstone reefs in the southeastern United States. Named in recognition of Milton B. Gray, a biological collector and curator at the University of Georgia Marine Institute, it is located 16 miles (17.5 nautical miles) off Sapelo Island, Georgia. Sanctuary boundaries protect 22 square miles of open ocean. The rocky platform, some 60 to 70 feet below the Atlantic Ocean's surface, is wreathed in a carpet of attached organisms and is known locally as a "live bottom habitat." Grouper, black sea bass, mackerel, angelfish and a host of other fish are attracted to the reef. Following close behind the schools of fish are the many sport fishing and diving enthusiasts who have made Gray's Reef one of the most popular recreation areas along the Georgia coast.

Florida Keys National Marine Sanctuary (FKNMS) supports one of the most diverse assemblages of underwater plants and animals in North America. Although best known for its coral reefs, the shallow waters near shore contain interconnecting and interdependent marine habitats that include fringing mangroves, seagrass meadows, hard bottom regions, patch reefs and bank reefs. This complex marine ecosystem is the foundation for the tourism and commercial fishing-based economies that are so important to Florida. Encompassing over 3,800 square miles of marine water surrounding the Florida Keys, this sanctuary supports over 6,000 species of marine life and protects shipwrecks and other important pieces of American maritime heritage. Visitors to the sanctuary are encouraged to enjoy the many recreational activities it has to offer, including world-class diving, swimming, snorkeling and kayaking.

Flower Garden Banks National Marine Sanctuary (FGBNMS) is located 70 to 115 miles off the coasts of Texas and Louisiana. The Flower Garden Banks were discovered by snapper and grouper fishermen in the late 1800's. They named the banks after the brightly colored sponges, plants and other marine life they could see on the colorful reefs below their boats. The sanctuary includes underwater communities that rise from the depths of the Gulf of Mexico atop underwater mountains called salt domes. Understanding the complexities of the sanctuary's local ecosystems requires learning about all of the components in its natural setting. This includes the underlying geology, a variety of habitats and the specific plants and animals found within the sanctuary. Visitors to FGBNMS can enjoy diving and fishing in the rich habitat that lies beneath the surface.