Coral Sea

Some reefs here sit on top of mountains under the sea.

One flat spot was even an island long ago.

Some Coral Sea reefs grow far out at sea, on top of underwater mountains called seamounts. Osprey Reef, more than 300 kilometers from Cairns, sits on a mountain that rises about 2,000 meters almost straight up from the ocean floor.

Other reefs cover flat-topped plateaus. NASA says the Bellona Plateau was a sizable island during the ice ages; today it lies 25 to 50 meters underwater, covered in corals and shelled animals.

Parks Australia describes Osprey Reef as the summit of a seamount rising almost vertically about 2,000 m from the ocean floor; the reef is almost 30 km long and more than 180 km² in area, with walls stepping down to 1,000 m. In 2009, the Deep Down Under expedition sent remotely operated vehicles to its undiveable depths and found stalked sea lilies and glass sponges.

NASA's Earth Observatory explains that the Bellona Plateau, about 600 km west of Grande Terre in New Caledonia, was a sizable island during the Pleistocene ice ages and is now under 25-50 m of water. Its corals, coralline algae, mollusks and foraminifera build carbonate skeletons and shells; in February 2023, Tropical Cyclone Gabrielle stirred up enough carbonate sediment to discolor more than 13,000 km² of water for about a week.

The Coral Sea reefs are far from land.

Many kinds of fish swim around them.

The Coral Sea Marine Park has 34 reefs scattered across it. Reefs make up only about 1 percent of the park, but that still adds up to 15,024 square kilometers. Surveys found nearly 600 kinds of fish.

Even though these reefs are only a few hundred kilometers from the Great Barrier Reef, their animals are more like those of faraway Pacific islands such as Tonga and Samoa.

Dive teams from Reef Life Survey made the first comprehensive surveys of the reefs in 2012 and 2013, at 17 reefs, recording nearly 600 fish species. Parks Australia reports that the reefs are the only places in Australia with fish, crustaceans and clams typical of oceanic Pacific islands, and that their communities resemble those of Tonga and Samoa, more than 2,500 km away, rather than the Great Barrier Reef a few hundred kilometers west.

Encrusting corals are the most widespread; reefs further south have denser coral cover, including branching corals and coral-dependent fishes such as butterflyfish.

Thousands of seabirds nest on the sandy islands.

Sea turtles, sharks and whales swim in the sea.

The Coral Sea's small coral islands, called cays, are home to busy seabird colonies. On one island, a Parks Australia-led team counted more than 40,000 pairs of nesting sooty terns, and the cays are also an important nesting area for red-tailed tropicbirds.

In the water live six of the world's seven kinds of sea turtle, sharks, barracuda and humpback whales. Parks Australia says the park has the only known spawning group of black marlin in the Pacific Ocean.

A Parks Australia-led island health voyage, with Queensland Parks and Wildlife, Tangaroa Blue and volunteer botanists, recorded globally significant nesting populations of sooty terns (one island with more than 40,000 nesting pairs), more than 690 breeding pairs of red-tailed tropicbirds, and 10 per cent of the global population of the endangered New Caledonia fairy tern nesting on one island.

Parks Australia lists six of the world's seven sea turtle species, sharks, barracuda, humpback whales and the only known spawning group of black marlin in the Pacific among the park's wildlife, and counts 341 species of international conservation significance. The Coringa-Herald and Lihou Reefs and Cays have been a Ramsar wetland of international importance since 2002.

If you see a turtle or a whale, stay back and just watch.

Never leave rubbish at the beach. Rubbish ends up even on faraway islands.

NOAA Fisheries asks people to watch sea turtles, whales, seals and other marine animals from a safe and respectful distance and never to touch them, for the animals' safety and yours.

Rubbish reaches even remote places. During one 12-day voyage in 2016, Parks Australia staff and volunteers collected more than 2 tonnes of rubbish from the Coral Sea Marine Park, from plastic bottles to fishing nets. Always take your rubbish home.

NOAA Fisheries urges people to observe marine animals from a safe and respectful distance and not to approach, touch or try to swim with them. In the Coral Sea, Parks Australia's island health voyages collect marine debris to learn what reaches remote cays and where it comes from: in June 2016, a 12-day voyage removed over 2 tonnes, and another voyage about 10 m³, including 240 m of plastic bottles laid end to end.

PlayOwl's own advice: on any boat trip, wear a life jacket and keep a grown-up close.