(CNNGo) -- It's been said that we know more about the moon than we know about our own oceans.
That's probably total rubbish. In any case the moon is about as interesting as a cold, hard ball of rock floating around empty space.
The oceans on the other hand can captivate even the most cynical of aesthetes. But they are fragile things.
Human activities such as overfishing and pollution threaten an estimated 88 percent of Southeast Asia's coral reefs. Recently Thailand's authorities closed 18 popular dive sites to allow them to recover from coral bleaching.
Here's a tour of 10 of Asia's most spectacular underwater dive sites, home to sharks, whales, sunfish and more, and a glimpse at some of the threats they face.
Pulau Sipadan, Malaysia
Pulau Sipadan is the only oceanic island in Malaysia, and before 2002 was the subject of an intense territorial dispute between Malaysia and Indonesia. It's rated by many dive journals as one of the top dive destinations in the world.
Recently, the Malaysian government has had to clamp down on coral thieves operating around the country's coastline.
Pulau Sipadan has also fallen victim to coral bleaching, a process most commonly caused by a change in sea temperature that "bleaches" the coral color.
One of the island's unique features is a turtle tomb, an underwater limestone cave that features many narrow tunnels and chambers containing the remains of green sea turtles (pictured) that have become trapped and drowned.
For more information visit Dive The World.
Similan Islands, Thailand
A clown fish, no stranger around the Similan Islands, is familiar to younger divers as "Nemo."
Clown fish engage in symbiotic relationships with sea anemones, eating invertebrates that might otherwise harm the anemone and providing sustenance for the anemone via their fecal matter.
With climate change acidifying oceans, which affects their sense of smell and obstructs their ability to find suitable anemones for shelter, clown fish are considered at risk.
For more information visti Similans.net.
Derawan Islands, East Kalimantan, Indonesia
Stingless jellyfish are some of the more unusual creatures to be found in the seas around the Derawan Islands, which consist of four inhabited islands and two uninhabited islands off the east coast of Borneo.
The jellyfish pictured here are foraging for food in Kakaban Lake on Kakaban Island.
Free from natural predators, the jellyfish lost their defence systems over thousands of years of evolution.
Being an enclosed environment however, life within Kakaban Lake is at risk from excessive human acitivty, such as outboard motor use.
For more information about Derawan Islands, visit Skin Diver Online.
Mergui Archipelago, Myanmar
Consisting of some 800 islands, the Mergui Archipelago is a largely desolate area, tucked away from the rest of the world. Popular with exploratory divers, it offers huge boulders, caverns, tunnels and drop-offs.
As well as sharks and manta rays, a diver might encounter red lionfish (pictured). Their spectacular frills conceal venomous spines on their backs. The spines are used for defense only.
When predating, lionfish rely on their quick reflexes to swallow prey whole.
Though the Andaman Sea has escaped much of the over-development, bleaching and nutrient loading that has affected other sites around the world, trawling, longline and blast fishing have impacted fish populations here.
For more information visit Mergui.org.
Raja Ampat Islands, Indonesia
Off the northwestern tip of Indonesia's West Papua province, the Raja Ampat Islands have the highest recorded diversity of fish and coral on earth -- an amazing 537 coral species and 1,074 fish species can be found here, according to The Nature Conservancy.
To date, the islands have been relatively resistant to coral bleaching and disease. They are credited with replenishing other reefs with coral larvae.
But overfishing, pollution and urbanization of coastlines threaten the reefs. The local government is working with agencies to protect the marine ecology while also supporting local livelihoods.
Pictured are fusilier fish, a common sight around Raja Ampat. These slick fish move sweepingly in a zig-zag pattern at high speeds and apparently in perfect unison, making them a truly remarkable thing to encounter.
For more information about Raja Ampat Islands, visit Diverajaampat.org.
Andaman Islands, India
The elusive ribboned sweetlips is one of the colorful habitants of the Andaman Islands. These fish can grow up to 50 centimeters in length. They live alone in deep water and feed on crabs, shrimps and sea snails.
Feeding is facilitated by their bright colors, which camouflages them against the corals.
To protect marine life that includes big game fish such as black marlin and sailfish, the Indian government has banned commercial fishing around the 572 islands that make up the Andaman Islands.
For more information about the Andaman Islands, visit Tourism.andaman.nic.in.
Komodo Island, Indonesia
The variety of marine life around Komodo Island ranges from sunfish, mantas, dolphins and eagle rays to the fascinating pygmy seahorses, ornate ghost pipefish and blue-ringed octopus, making this one of the most diverse and vibrant dive spots on the planet.
In past years dynamite fishing and a crown of thorns infestation severly traumatized the reef system, and artificial electric reefs were introduced to help rebuild the coral.
For more information about Komodo Island, visit Dive The World.
Tulamben, Bali, Indonesia
The small fishing village of Tulamben hosts one of the most popular dive sites on Bali. During World War II, a Japanese torpedo sank the USAT Liberty, a U.S. Army transport ship.
The 120-meter-long wreck is now home to a variety of fish species, such as batfish, angelfish, puffer fish and hawkfish.
Fishing is banned in the area around Tulamben and some resorts have undertaken voluntary eco-initiatives, but the number of visitors to the site -- up to 100 divers per day during peak periods -- is a potantial threat.
For more information about the Tulamben Island, visit Sea Focus.
Kerama Islands, Okinawa, Japan
The Kerama Islands are host to 76 dive sites, and are relatively well protected thanks to a local community that has embraced both its natural oceanic ecosystems and tourism.
The Akajma Marine Science Laboratory on Akajima Island (population 300) was founded in 1988 and has provided data and guidance for the whole of Japan on the conditions and best protective practices for its reef systems.
Cuttlefish (pictured) are one of the many sea species that can be seen around the islands, along with larger creatures such as humpback whales and manta rays. Despite their name, cuttlefish are not fish but molluscs, and can change color rapidly to camouflage themselves when danger is near.
For more information about Kerama Islands, visit Open Coast.
Tubbataha Reef National Marine Park, Philippines
Declared a world heritage site by UNESCO in 1993, the Philippines' Tubbataha Reef National Marine Park is crawling with marine life. Sharks, turtles and reef fish can often be found congregating around the atoll.
The UN describes the area as "a pristine coral reef with a spectacular 100-meter perpendicular wall, extensive lagoons and two coral islands."
With shipping, marine pollution and oil exploration efforts disrupting the natural habitats, many species here are endangered.
It is hoped that a "buffer zone" around the most sensitive parts of the reef, as well as more effective enforcement of anti-littering marine laws, will enhance the longevity of many of these threatened species.
For more information about Tubbatha Reef National Marine Park, visit Tubbatahareef.org.
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