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  • In the north-east of the Indian Ocean,

  • spanning a latitude of 6 to 16 degrees north of the Equator,

  • lies the Andaman Sea.

  • For the people of Thailand and Burma, also known as Myanmar,

  • the two nations bordering the eastern edge of the Andaman,

  • the sea has always been an integral part of life and the economy.

  • The Andaman's warm waters support an enormity of marine life

  • and they are relied upon for food as well as transport.

  • Limestone formations such as those which make up the Phi Phi Islands

  • contrast with granite outcrops like the Similan Islands.

  • The warm, clear water and diversity of marine life

  • make the Andaman an attractive dive destination

  • and many divers visit each year to explore and enjoy the underwater world.

  • And seldom is the marine landscape as diverse as it is here.

  • Millions of years of decay have cut the limestone pinnacles of Burma's Mergui Archipelago

  • into a terrain of underwater canyons and caves.

  • Further south, the huge granite boulders of Thailand's Similan Islands

  • continue beneath the waterline,

  • creating dramatic caves and swim-throughs.

  • Much of the submerged rock has been colonized by soft corals

  • like this mushroom leather coral at Christmas Point

  • or stony corals like this field of staghorn coral at Koh Bon

  • or this Montipora coral at East of Eden.

  • Elsewhere magnificent anemones have taken over.

  • At shallow sites such as Richelieu Rock the ebb and flow of the tide

  • brings the oxygen necessary for turtle weed, a type of green algae, to flourish.

  • Dendronephthya soft corals adorn the valleys and slopes at Hin Muang, or "purple rock" in Thai.

  • Elsewhere pretty crinoids, or "feather stars",

  • take up prime positions for filtering plankton from the water.

  • A feeding strategy shared by giant sea fans,

  • whose sieve-like skeleton makes them highly efficient filter feeders.

  • Here between the rocks and coral lie leopard sharks.

  • These gentle creatures are quite the opposite of many people's impression of the fearsome shark.

  • Rather than sharp teeth, their mouths contain ridged plates.

  • Leopard sharks can be easily and safely approached

  • but if divers get too close they will finally make their departure.

  • Although "leopard shark" is the most commonly used name in the Andaman Sea,

  • globally, these sharks are more commonly known as "zebra sharks",

  • because the rarely seen juveniles have stripes, not spots.

  • Bearing many similarities to leopard sharks,

  • nurse sharks are also normally placid.

  • Like leopard sharks they don't have sharp teeth.

  • Nurse sharks should be treated with respect however.

  • They have been known to bite divers when provoked,

  • and if they bite they tend not to let go.

  • During the day, tawny nurse sharks are normally found sleeping under ledges,

  • often piled up in groups like here at Koh Bon Pinnacle.

  • Although nurse sharks generally feed at night,

  • here at the Burma Banks they are often on the prowl looking for food during the day time too.

  • They have 2 barbels above the mouth which help them probe for food.

  • When the shark senses prey such as small fishes or crustaceans

  • it uses a strong sucking action to draw the food into the mouth.

  • Bonds between nurse sharks appear to be closer than with many other shark species

  • and they are often seen swimming in couples.

  • At Thailand's Richelieu Rock, a whale shark makes a rare appearance.

  • This is no whale but rather the world's largest fish.

  • Whale sharks can grow up to 12 meters long,

  • although unconfirmed reports circulate of giants up to 18 meters long.

  • This female is about the average size of 8 meters.

  • There is little to match the awe inspired by an encounter with a whale shark,

  • and for many divers this is the pinnacle of their underwater experience.

  • Their 3000 tiny teeth are rarely used.

  • When feeding they hold their mouths open

  • and feed on plankton, fish eggs and small marine creatures.

  • Ridges down the whale shark's back are reminiscent of those on zebra sharks' backs

  • and like the zebra shark, the whale shark poses little danger to humans.

  • She has lost the top part of her tail,

  • perhaps due to an attack by a predatory shark when she was a youngster,

  • or possibly a collision with a boat's propeller.

  • The shark's fins act like rudders,

  • helping steer it gracefully through the water.

  • For a long time whale sharks were thought to be oviparous,

  • in other words hatching from eggs laid by the mother.

  • However since 1995,

  • females have been discovered containing hundreds of hatched pups,

  • proving that the young complete their development inside the mother's body before birth.

  • As is typical of large pelagic fishes, the back is darker than the belly.

  • This countershading helps it blend in with its environment,

  • and the abstract pattern of spots and stripes on the back enhances the camouflage from above.

  • Some whale sharks attract shoals of fish around the head,

  • such as these juvenile scad,

  • protecting themselves from predators which may be intimidated by the shark.

  • The shark itself does not prey on them,

  • and they are careful enough to cruise in front of its cavernous mouth,

  • without getting sucked in.

  • This much younger whale shark approached boats near Western Rocky Island

  • and stayed around for a long time.

  • Although it might be tempting to touch or even hitch a ride on a whale shark,

  • this practise is highly discouraged.

  • It may modify the shark's natural behavior, or even cause infection.

  • It can also be dangerous for the diver or snorkeler.

  • Despite their usual graceful and stately motion,

  • whale sharks can draw on great strength if they become agitated,

  • and should be respected like any wild animal.

  • Shark fin soup is seen as a delicacy and status symbol in many Asian markets.

  • A single whale shark fin can fetch tens of thousands of dollars in some Chinese restaurants,

  • and often a whale shark fin is not eaten

  • but just used to advertise the availability of shark fin or shark fin soup.

  • Whale sharks do not reach sexual maturity until they are 25 years old,

  • and pregnancies are few and far between,

  • so their survival is particularly at risk.

  • Unless this culture changes,

  • or legislation is introduced and enforced,

  • whale sharks, like many other sharks,

  • may soon disappear forever.

  • From the shadows, and shoals of cardinalfish

  • at Burma's Shark Cave,

  • a grey reef shark emerges.

  • This strong stocky shark feeds mainly at night,

  • but may sometimes be seen cruising during the day.

  • The canyon at Shark Cave provides an excellent viewing gallery.

  • Although grey reef sharks can sometimes show aggression in their behaviour,

  • this is extremely rare amongst those found in the Andaman.

  • A visit to the Burma Banks will sometimes yield an interesting encounter with silvertip sharks.

  • These juveniles are particularly curious of divers.

  • As adults they will grow larger than grey reef sharks,

  • up to 3 meters in fact,

  • but they will also withdraw slightly

  • and become more wary of close human contact.

  • Already these young silvertips display the streamlined body and attractive coloration

  • that make them a favorite amongst shark lovers.

  • One of the most common sharks to be found across the Andaman Sea

  • is the whitetip reef shark.

  • Because of similar coloration of the dorsal and tail fins,

  • the whitetip reef shark and silvertip shark are sometimes confused,

  • but the whitetip has a wedge-shaped head,

  • and it's cigar-shaped body is slimmer than the silvertip's.

  • Black Rock, on the western edge of the Mergui Archipelago,

  • is one of the area's best dive sites,

  • and whitetip reef sharks are commonly encountered during the descent.

  • The other main order of cartilaginous fishes to be found

  • around the Andaman's reefs is the rays,

  • and most common of these is the bluespotted stingray.

  • This stingray's coloration and common name

  • make it often confused with the more circular blue-spotted stingray

  • found in the Gulf of Thailand,

  • which belongs to a different genus.

  • The bluespotted stingray is found on sandy bottoms

  • at sites such as East of Eden in the Similans.

  • The neutral color of the larger Jenkins whipray

  • camouflages it well against the seabed.

  • This ray has a pair of sharp and venomous spines near the base of its tail,

  • and the name "whipray" comes from the ray's ability to whip it's long tail over fast

  • and administer a nasty sting to a predator at any part of its circumference.

  • The ray takes water in through its spiracle, a hole just behind the eye.

  • This water can be blown out through the mouth

  • to excavate food from the substrate.

  • Another large stingray common to the area is the blotched fantail ray.

  • This impressive species can grow nearly 2 meters in diameter

  • and is often one of the highlights of dives in the Andaman.

  • Blotched fantail rays are most impressive when they aggregate in shoals.

  • Occasionally they can be witnessed in large numbers.

  • I encountered this shoal of some 30 individuals at Black Rock.

  • They had possibly gathered to mate.

  • Another visitor to Black Rock and other deep-water sites is the spotted eagle ray.

  • In some parts of the world eagle rays stay together in schools.

  • In the Andaman Sea they are normally found alone.

  • Just behind the short dorsal fin they have up to 6 venomous tail spines

  • which can inflict serious damage on attackers.

  • Between its wing-like fins it has a solid, heavy body and a deep head.

  • The smoothtail mobula is a similar size to the eagle ray

  • but can only usually be seen by divers in the northern Andaman

  • at sites like Burma's Tower Rock,

  • although they are occasionally seen in Thailand

  • at sites such as Racha Noi.

  • The mobula is a member of a group termed "devil rays",

  • so named because of 2 protruding cephalic fins either side of it's mouth.

  • These fins help to direct plankton and small marine creatures

  • into the mouth for feeding.

  • The mobula is a highly social fish

  • and is often observed in large schools.

  • The mobula is an impressive sight

  • but shares our seas with a much larger devil ray:

  • the king of all rays, the giant manta ray.

  • Mantas are frequent visitors to sites such as Koh Bon.

  • Giant mantas can grow to a width of over 6 meters

  • and a weight of over 2 tonnes.

  • These pelagic fish are always on the move

  • and like mobulas, they feed by swimming open-mouthed

  • and using the 2 cephalic fins to direct water into the mouth.

  • The gills on its white underside contain rakers

  • which filter out plankton and small organisms.

  • The markings on the back and underside of mantas are highly variable

  • and are useful in distinguishing individuals.

  • Occasionally the cephalic fins are furled up into cylinders to improve streamlining.

  • Mantas are one of the most intelligent fish,

  • with the largest brain-to-body mass ratio of all elasmobranchs.

  • They often seem to enjoy interaction with humans.

  • A gentle approach by divers is often permitted,

  • and mantas will sometimes approach divers,

  • apparently out of curiosity.

  • Mantas only give birth to an average of two pups every two years,

  • and populations have long been in decline.

  • The gill rakers of mantas and mobulas are used in a Chinese medicine

  • that is thought to detoxify the blood.

  • There is no scientific evidence that it works.

  • Nevertheless the lucrative trade is on the increase.

  • In November 2011

  • the International Union for Conservation of Nature

  • declared giant manta rays as "vulnerable with an elevated risk of extinction".

  • Down on the reef, a fish trap has caught a handful of bony fishes

  • including a giant moray eel.

  • This is the largest of all morays.

  • Despite their fearsome appearance,

  • morays are not as dangerous to humans as they look,

  • although larger morays can attack if provoked

  • and have been known to bite divers when being fed.

  • The mouth contains sharp teeth for capturing and restraining prey.

  • Once captured, a second set of jaws in the throat

  • is launched forward to grab the prey

  • and pull it down the moray's gullet.

  • Anemone Reef is home to several specimens of yellow-edged moray.

  • Like many morays they feed on small reef fishes.

  • Khao Lak's Boonsung tin miner wreck

  • has a particular concentration of honeycomb morays.

  • This spotted moray at the Burma Banks is a close relative.

  • Whitemouth morays are not at all common in the Andaman.

  • This rare specimen was seen at Burma's Western Rocky Island.

  • Another Myanmar speciality is the barredfin moray.

  • When feeling threatened it adopts a very snake-like posture.

  • Facial injuries are quite common amongst morays,

  • and this palechin moray at High Rock bears the scars of past conflicts.

  • The cartoon-like features of the greyface moray

  • are much more common throughout the area

  • and these eels are often found in pairs or small groups.

  • This is a small and very energetic species

  • and when it attacks it moves quickly.

  • Greyface morays don't just live with each other;

  • they often share their home with other species.

  • In this case a fimbriated moray.

  • And here we find a fimbriated moray with a snowflake moray.

  • Whereas the previous species feed mainly on fishes,

  • the snowflake moray feeds on shelled molluscs and crustaceans,

  • so it's teeth are much more blunt.

  • It's not difficult to see how the zebra moray got its name.

  • This moray also feeds on crustaceans.

  • Of all the marine creatures found in the Andaman Sea,

  • possibly the tiger tail seahorse carries the most mystique.

  • The seahorse finds a suitable holdfast,

  • such as this black sun coral,

  • and anchors itself to it using its striped tail.

  • Here at Shark Cave a seahorse has become stuck to a worm sea cucumber.

  • The seahorse struggled for several minutes

  • before finally freeing itself from the sea cucumber's adhesive body.