The Península Valdés in Argentina was inscribed on the World Heritage List in 1999. The site is home to important breeding populations of the endangered southern right whale (Eubalaena australis), southern elephant seal (Mirounga leonina), and southern sea lion (Otaria flavescens), pictured here.

A small giant clam -- yes, that's it's real name -- in Australia's Great Barrier Reef.

The Heard & McDonald Islands site in Australia was inscribed on the World Heritage List in 1997. As the only volcanically active sub-Antarctic islands, Heard and McDonald provide the opportunity to observe ongoing geomorphic processes and glacial dynamics. The distinctive conservation value of these pristine islands is the complete absence of introduced plants and animals – or any other human impact – which makes this site ideal breeding grounds for animals like the southern elephant seal (Mirounga leonina) and king penguins (Aptenodytes patagonicus), pictured here.

The Macquarie Island site in Australia was inscribed on the World Heritage List in 1997. The island is the exposed crest of the undersea Macquarie oceanic ridge, raised to its present position where the Indo-Australian tectonic plate meets the Pacific plate. It is a site of major geo-conservation significance, with exposures that include excellent examples of pillow basalts and other extrusive rocks. The island is used by a number of animals, including southern elephant seals, sub-Antarctic fur seals, albatross, giant petrels, and king penguins.

The Shark Bay site in Australia was inscribed on the World Heritage List in 1991. The site is home to the world's richest and largest sea-grass beds; five species of endangered marine mammals, including dugongs (Dugong dugon), which feed on the grass; and stromatolites, dome-shaped structures created by cyanobacteria, one of the oldest forms of life on earth.

The Sundarbans site in Bangladesh, which was inscribed on the World Heritage List in 1997, includes one of the largest remaining areas of mangroves in the world and supports a rich animal community.

The Belize Barrier Reef Reserve System site in Belize was inscribed on the World Heritage List in 1996. The site is an outstanding natural system, consisting of the largest barrier reef in the northern hemisphere, offshore atolls, and several hundred sand cays, mangrove forests, coastal lagoons, and estuaries. The system's seven sites illustrate the evolutionary history of reef development and are a significant habitat for threatened species, including marine turtles, manatees, and the American marine crocodile.

The Brazilian Atlantic Islands site was inscribed on the World Heritage List in 2001. The rich waters of the Fernando de Noronha Archipelago and Rocas Atoll are extremely important for the breeding and feeding of tuna, shark, turtle, and marine mammals. The site is home to the largest concentration of tropical seabirds in the Western Atlantic. Baia de Golfinhos has an exceptional population of resident dolphin, and at low tide, the Rocal Atoll provides a spectacular seascape of lagoons and tidal pools teeming with fish.

The Kluane / Wrangell-St Elias / Glacier Bay / Tatshenshini-Alsek site in Canada and the United States was inscribed on the World Heritage List in 1979. The sites protected areas along the boundary of Canada and the United States of America are the largest non-polar ice-field in the world and contain examples of some of the world's longest and most spectacular glaciers. Characterized by high mountains, ice-fields and glaciers, the site transitions from northern interior to coastal biogeoclimatic zones, resulting in high biodiversity with plant and animal communities ranging from marine, coastal forest, montane, sub-alpine, and alpine tundra, all in various successional stages.

The Malpelo Fauna and Flora Sanctuary site in Colombia was inscribed on the World Heritage List in 2006. The marine park surrounding Malpelo Island is the largest no-fishing zone in the Eastern Tropical Pacific, providing critical refuge for threatened and endangered marine mammals, fish, and turtles. The nutrient-loaded waters support rich aggregations of biodiversity, including populations of large predators like the hammerhead shark (Sphyrna lewini), pictured here, and is an important source of fish and invertebrate larvae to surrounding waters.

A leatherback sea turtle crawls across the sand at the Area de Conservación Guanacaste site in Costa Rica.

The Cocos Island National Park site in Costa Rica was inscribed on the World Heritage List in 1997. Cocos Island’s position as the first point of contact with the northern equatorial counter-current and the myriad interactions between the island and the surrounding marine ecosystem make the area an ideal laboratory for the study of biological processes. The site hosts critical habitats for marine wildlife, including large pelagic species, especially sharks (like the hammerhead Sphyrna lewini), but also rays, tuna, and dolphins.

The Galápagos Islands site in Ecuador was inscribed on the World Heritage List in 1978. Located in the equatorial Pacific Ocean nearly 1000 km from South America, the Galapagos Islands and the surrounding marine reserve are a unique “living museum and showcase of evolution.” Ongoing seismic and volcanic activity reflect the processes that formed the islands, which together with the extreme isolation, led to the development of unusual animals, such as the land iguana, giant tortoise, and the many types of finch – all of which inspired Charles Darwin’s development of the theory of evolution by natural selection, following his visit in 1835. Pictured here is the Sally lightfoot crab, Grapsus grapsus.

The Gulf of Porto: Calanche of Piana, Gulf of Girolata, Scandola Reserve site in France was inscribed on the World Heritage List in 1983. The site's vegetation is an outstanding example of scrubland. Seagulls, cormorants, and sea eagles can be found here, while the clear waters, with their islets and inaccessible caves, host a rich and diverse marine life.

The Lagoons of New Caledonia: Reef Diversity and Associated Ecosystems site in France was inscribed on the World Heritage List in 2008. The site features an exceptional diversity of coral and fish species and a continuum of habitats from mangroves to seagrasses, with one of the world's most diverse concentrations of reef structures. The lagoons also provide habitat to a number of emblematic or threatened marine species such as giant grouper, black-spotted stingray, several species of sharks, whales, dolphins, turtles, and the third largest population of dugongs in the world.

The Wadden Sea site in Germany and the Netherlands was inscribed on the World Heritage List in 2009. It hosts marine mammals, including the harbor seal Phoca vitulina, pictured here.

A grey seal at Iceland's Surtsey Island, a World Heritage site. Surtsey is unique because it’s been protected since its formation in the 1960's, providing the world with a pristine natural laboratory.

The Sundarbans National Park site in India, which was inscribed on the World Heritage List in 1987, contains the world's largest mangrove forest and hosts a number of rare and endangered species including tigers, aquatic mammals, birds, and reptiles.

The Komodo National Park site in Indonesia was inscribed on the World Heritage List in 1991. The site hosts “Komodo dragons” (Varanus komodoensis), a unique species that exists nowhere else in the world and is of great interest to scientists studying evolution. The rugged hillsides of dry savannah and pockets of thorny green vegetation contrast starkly with the brilliant white sandy beaches and blue coral-rich waters offshore. Pictured here is some of the diversity of marine life in the park: three species of tunicates (“sea squirts”) – Polycarpa aurata is purple and orange, Atriolum robustum is green, and the blue is from the genus Rhopalaea.

The coral reefs of Ujung Kulon National Park in Indonesia, a World Heritage site, are dominated by a small number of coral species and support some of the richest fish fauna in the Indonesian archipelago.

Steller’s sea eagles, a threatened species, gather on sea ice at the Shiretoko Peninsula in Japan.

The Phoenix Islands Protected Area site in Kiribati was inscribed on the World Heritage List in 2010. The site encompasses one of the world's largest intact oceanic coral archipelago ecosystems, together with 14 known underwater seamounts and other deep-sea habitats. There are about 200 coral species, 500 fish species, 18 marine mammals, and 44 kinds of birds. The structure and functioning of the site's ecosystem illustrates its pristine nature and importance as a migration route and reservoir of organisms to surrounding exploited areas. Pictured here is a school of ornate butteryfly fish (Chaetodon ornatissimus), one of the many colorful fish protected within the boundaries of the site.

The Banc d'Arguin National Park site in Mauritania was inscribed on the World Heritage List in 1989. Fringing the Atlantic coast, the park comprises sand dunes, coastal swamps, small islands, and shallow coastal waters. A wide variety of migrating birds spend the winter, while several species of sea turtle and dolphin, used by fishermen to locate shoals of fish, can also be found here.

The Islands and Protected Areas of the Gulf of California site in Mexico was inscribed on the World Heritage List in 2005. The site is important for its diversity of oceanographic processes, including wind- and current-driven upwelling, tidal mixing, and hydrothermal vents – all of which contribute to its extraordinary biological diversity. There are 890 fish species (90 of which occur nowhere else), 34 kinds of whales and dolphins, 25 species of coral, over 4,800 invertebrates, the poisonous yellow-bellied sea snake, and 90% of the world’s Heermann’s gulls. Within the site are breeding and nursery grounds for 30,000 California sea lions (Zalophus californianus), as well as feeding and wintering grounds for five of the world’s eight species of marine turtles: leatherback, hawksbill, loggerhead, black or Pacific green, and olive ridley.

The Sian Ka’an site in Mexico was inscribed on the World Heritage List in 1987. The site’s name means “Origin of the Sky” in Mayan and contains tropical forests, mangroves, and marshes, as well as a large marine area intersected by the Caribbean Barrier Reef. On land there are 1,200 plant species, five species of felines (including jaguars and ocelots), as well as threatened tapirs and peccaries. Aquatic animals include manatees (Trichechus manatus) and nesting colonies of jabiru storks (Jabiru mycteria), frigate birds (Fregata magnificens), brown pelicans (Pelecanus occidentalis), and roseate spoonbills (Platalea ajaja).

The Whale Sanctuary of El Vizcaino site in Mexico was inscribed on the World Heritage List in 1993. The sanctuary contains important breeding and wintering sites for the grey whale (Eschrichtius robustus – pictured here), harbor seal (Phoca vitulina), California sea lion (Zalophus californianus), northern elephant seal (Mirounga angustirostris), and blue whale (Balaenoptera musculus). The lagoons are also home to four species of endangered marine turtles: leatherback (Dermochelys coriacea), green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and olive ridley (Lepidochelys olivacea).

The New Zealand Sub-Antarctic Islands site was inscribed on the World Heritage List in 1998. The islands are particularly notable for the abundance and diversity of nesting pelagic seabirds and penguins (including macaroni penguins, Eudyptes chrysolophus, pictured here). There are over 120 bird species in total, including 40 seabirds, five of which breed nowhere else. The islands support major populations of 10 of the world’s 24 species of albatross. And almost 6 million sooty shearwaters (Puffinus griseus) nest on Snares Island alone.

The West Norwegian Fjords – Geirangerfjord and Nærøyfjord site was inscribed on the World Heritage List in 2005. The site's two fjords, among the world's longest and deepest, are considered archetypical fjord landscapes and among the most scenically outstanding anywhere. Their exceptional natural beauty is derived from narrow and steep-sided crystalline rock walls that rise up to 1,400 m from the Norwegian Sea and extend 500 m below sea level. The site features geological structures such as submarine moraines (undersea remnants of glacial activity), as well as colonies of seals (Phoca vitulina) and porpoises (Phocoena phocoena).

A school of blue-striped snapper gathers at Coiba National Park and its Special Zone of Marine Protection site in Panama.

The Puerto-Princesa Subterranean River National Park site in the Philippines was inscribed on the World Heritage List in 1999. The site’s topography varies from flat plains to rolling hinterlands and hills to mountain peaks, encompassing a complete mountain-to-sea ecosystem and providing significant biodiversity conservation habitat. One of the park’s unusual features is its spectacular limestone karst landscape (shown here), with its underground river emerging directly into the sea.

The Tubbataha Reefs National Park site in the Philippines was inscribed on the World Heritage List in 1993. The site is an example of a pristine coral reef with a spectacular 100 m (330 ft) perpendicular wall, extensive lagoons, and two coral islands – all of which supports a diverse marine community. The waters surrounding the atolls provide refuge to several hundred species of fish (including 11 types of shark), 46 kinds of coral, and 11 cetaceans (whales and dolphins). The park’s land area provides nesting grounds for seven species of seabird, as well as the endangered hawksbill and green turtles (Eretmochelys imbricata and Chelonia mydas).

The Natural System of Wrangel Island Reserve site in Russia was inscribed on the World Heritage List in 2004. Located well above the Arctic Circle, the site includes the mountainous Wrangel Island, Herald Island, and surrounding waters. The reserve has exceptionally high levels of biodiversity and boasts the world's largest population of Pacific walrus (Odobenus rosmarus divergens – pictured here) and the world’s highest density of ancestral polar bear dens (Ursus maritimus). It’s also an important feeding ground for gray whales (Eschrichtius robustus) migrating from Mexico and is the northernmost nesting ground for 100 migratory bird species, many of which are endangered.

The Aldabra Atoll site in the Seychelles was inscribed on the World Heritage List in 1982. The site is comprised of a coral reef surrounding four large coral islands, which enclose a shallow lagoon. Protected from human influence, Aldabra’s beaches are safe nesting habitat for hawksbill turtles (Eretmochelys imbricata – pictured here), one of the Indian Ocean’s largest congregations of nesting green turtles (Chelonia mydas), and the world’s second largest breeding populations of greater and lesser frigate birds (Fregata minor & Fregata ariel). The site also provides a refuge to 100,000 Aldabran giant tortoises (Dipsochelys dussumieri), one of the few surviving giant tortoise species of the Indian Ocean region.

The East Rennell site in the Solomon Islands was inscribed on the World Heritage List in 1998. The site contains one of the largest raised coral atolls in the world, with a marine area extending three nautical miles to sea. The strong climatic effects of frequent cyclones make the area a true natural laboratory for scientific study. However, there is currently little detailed information available about the marine regions within the site.

The iSimangaliso Wetland Park site in South Africa was inscribed on the World Heritage List in 1999. Wind and water continue to shape the site’s diverse landforms: coral reefs, long sandy beaches, coastal dunes, lake systems, swamps, and extensive reed and papyrus wetlands. As a result, the park contains critical habitat for an exceptional diversity of species from Africa's marine, wetland, and savannah environments. Pictured here is a whale shark (Rhincodon typus), which ranges between shallow near-shore and deeper offshore waters.

The Ibiza, Biodiversity and Culture site in Spain was inscribed on the World Heritage List in 1999. The site’s dense prairies of Posidonia oceanica, an important (and highly productive) endemic sea grass, provide coastal protection from storms, food and habitat for a broad diversity of marine life, and critical nursery grounds for fishery species. Among the site’s other significant marine values are underwater caves that offer access to important geological features, the most diverse pillow coral community (Cladocora caespitosa) in the Mediterranean, and a valuable population of Ecteinascidia turbinata, a tunicate or “sea squirt” with recognized use in preventing and treating cancer. Ibiza also offers protection to three globally endangered species, including the Mediterranean monk seal (Monachus monachus).

The High Coast in Sweden and the Kvarken Archipelago in Finland were inscribed on the World Heritage List in 2000. The High Coast and the 5,600 islands of the archipelago have been shaped by the combined processes of glaciation, glacial retreat, and the emergence of new land from the sea, as the weight of the glacial ice is removed by melting (“isostatic uplift”). The special feature of the site’s marine realm is that it’s the submarine extension of the landscapes undergoing such uplift. Continual elevation of the land results in inlets becoming progressively cut off from the sea, transforming them into estuaries and ultimately lakes. Meanwhile, shorelines are constantly reshaped, new islands are born offshore, and others become peninsulas as they unite with the mainland.

The Gough and Inaccessible Islands site in the United Kingdom was inscribed on the World Heritage List in 1995. The site, located in the south Atlantic, is one of the least-disrupted island and marine ecosystems in the cool temperate zone. The spectacular cliffs, towering above the ocean, are free of introduced mammals and home to one of the world's largest colonies of sea birds, including millions of great shearwaters (Puffinus gravis). Southern elephant seals (Mirounga leonina) have only occasionally been sighted on shore, but there is a large breeding population of sub-Antarctic fur seals (Arctocephalus tropicalis – pictured here), as well as 10 percent of the global population of northern rockhopper penguins (Eudyptes moseleyi).

The volcanic archipelago St. Kilda in the United Kingdom has some of the highest cliffs in Europe and hosts large colonies of endangered seabirds.

The Everglades National Park in the United States was inscribed on the World Heritage List in 1979. This site is a unique ecosystem created by a shallow, “imperceptible river” 50 miles wide, flowing slowly south to the tip of Florida. The exceptional variety of aquatic habitats has made it a sanctuary for a large number of birds and threatened species such as American crocodiles (Crocodylus acutus) and Florida manatees (Trichechus manatus latirostris). Pictured here is a great egret (Ardea alba) standing among cypress trees (Taxodium).

The Papahānaumokuākea site in the United States was inscribed on the World Heritage List in 2010. The site is a vast isolated cluster of small low-lying islands and atolls with its surrounding ocean. Apart from the deep cultural significance the site has for living Hawai'ians, it’s important for its pelagic and deepwater habitats, which contain special features such as seamounts, submerged banks, and extensive coral reefs and lagoons, providing safe habitat for endangered species like the green sea turtle (Chelonia mydas), pictured here.

The Ha Long Bay site in Vietnam was inscribed on the World Heritage List in 1994. The site’s 1,600 islands and islets form a spectacular seascape of limestone pillars surrounded by species-rich waters, including a tremendous diversity of marine algae and over a thousand varieties of fish.

A Socotra cormorant dries its wings on the shore at the Socotra Archipelago in Yemen.