CARREY: The islands of Papua New Guinea and Indonesia.
Here, volcanic gases form undersea fountains...
and the sea erupts with kaleidoscopic life.
The reefs surrounding these Pacific Islands form the heart of the Coral Triangle.
More marine species live here than anywhere else on Earth.
So many species live here that they can all survive...
only if each is distinctly different from the other.
This puppy-like creature is actually an epaulette shark...
who lives only in the Coral Triangle.
He's not much of a swimmer, so he prefers to crawl.
The Wobbegong Shark looks like a shag carpet...
until he moves.
Disguised hunters need almost endless patience.
Dinner must come to them.
A giant frogfish is hoping the school of glassy sweepers...
mistakes it for a yellow sponge.
The crocodile fish blends into the reef perfectly.
This time, the Blue Damselfish was lucky.
But out of the frying pan and into the fire.
Giant frogfish come in all colors.
Trying to hide under one could be a really bad idea.
The stonefish is about as graceless as a fish can be.
It has little to fear from predators.
No fish on Earth is more venomous.
It might wait several days for a careless fish...
to swim within range of that big ugly mouth.
After waiting so patiently...
that must be frustrating.
But the most venomous creatures here are not fish.
That distinction belongs to sea snakes.
Their venom is many times more potent than a king cobra's.
Like other snakes, these breathe air...
but they can dive more than 100 feet, and stay down for hours.
Sea snakes are increasingly rare, even here in the Coral Triangle.
Most have become wallets, shoes or handbags.
In the Coral Triangle, mangroves fringe most shorelines.
These coastal jungles protect islands from erosion...
and provide a buffer against storms and even the occasional tsunami.
The labyrinth of mangrove roots...
captures sediments washed down from the islands...
keeping the coral reef from being smothered in silt.
The maze of roots is a shadowy habitat for many creatures.
A swarm of Striped Catfish feeds on algae growing on the roots...
and on the silty bottom.
This silt settles in bays...
forming vast plains of organic debris, sand and muck.
And if you think nothing could live here, you might be surprised.
The catfish school cascades across the mucky bottom like a breaking wave...
as fish feeding in the front are passed over by those in the rear.
Like most animals living here...
the stingray conceals itself by hiding beneath the muck.
Dude, I can totally see your tail.
The goby is an excellent watchman, but not so good at cave building.
He leaves the heavy construction to his partner and personal contractor...
the nearly-blind shrimp.
The relationship is called symbiosis.
Both animals think they have a pretty good deal.
A carrier crab is looking for his own symbiotic partner.
He's happy to find a jellyfish...
which he decides to wear as a protective hat.
This is a love triangle.
Flamboyant Cuttlefish.
The 2 small ones are the hopelessly devoted males.
The female is the larger one, but they would never tell her that.
They can swim well enough, but usually prefer to gallop across the muck...
on the tips of their fleshy, little arms.
Their mating embrace is little more than a peck on the cheek.
The male simply passes the female a tiny packet.
Or, at least he tries to.
Whether she'll accept is another matter.
That's all there is to it.
Deeper in the bay, a school of reef squid...
fashion a bouquet of translucent egg cases.
Male squid hover nearby as females move in...
and add to the cluster.
In about 3 weeks, the egg casings will begin to burst...
each releasing a half a dozen or so jewel-like miniatures.
The baby squid will then drift away across the sandy plain...
to take their chances.
A field of garden eels towers over the sea floor.
Some rise more than 6 feet...
reaching high to snap up tiny animals adrift in the current.
Above the reef, a swarm of baby convict fish forages over the coral.
Then, in late afternoon, they all gather over a burrow in the sand...
that serves as home.
The dark creature emerging from the borough is an adult convict fish.
Her brief appearance may be a signal, beckoning her children home for the night.
But before sleeping, the babies have one important chore:
They must feed their parents.
The pair of adult convict fish never leave their den.
And what they eat is a mystery.
Some scientists believe the babies feed their parents a form of secreted slime.
But others think mom and dad survive...
simply by eating a few of their children every night.
As evening deepens, reef cuttlefish are on the hunt.
They communicate with instantaneous changes of color, pattern and texture.
Their ability to hover without effort...
is aided by a porous calcium-carbonate structure beneath their skin.
This cuttlebone gives the creature buoyancy.
Cuttlefish are aggressive hunters.
They strike with blinding speed...
shooting out a pair of lightning fast tentacles.
A piercing tongue covered with razor-sharp teeth...
waits to gnaw the fish to bits.
South of the Coral Triangle lies the largest living structure on Earth...
Australia's Great Barrier Reef.
This most recent version of the Great Barrier Reef...
began growing about 12,000 years ago...
at the end of the last Ice Age.
Then, sea levels were 400 feet lower than they are today.
As the ice began to melt, the seas rose.
Corals grew on top of coral...
building undersea mountains made of limestone or calcium carbonate.
Corals grow by combining carbon dioxide and sunlight.
But the balance of carbon dioxide in our atmosphere is critical...
especially to coral reefs, and the creatures that call them home.
Every animal here depends on another in some fashion.
This potato cod is ready for her beautician.
And let's face it, when you're a cod, you need all the help you can get.
Cleaner fish provide a gentle service no self-respecting cod can be without.
While giving her a facial, the cleaners eat parasites.
And in exchange, the potato cod resists the temptation to gobble them up.
Another good deal.
A crown jellyfish slowly pulsates...
forcing tiny animals to pass through its stinging tentacles.
When the current carries a jellyfish into the reef...
butterfly fish join up.
Even if it makes their little lips sting.
Some creatures are not satisfied with only a taste.
Green sea turtles love to fill their cast-iron stomachs with venomous jelly.
As the turtle devours its prey...
it carefully closes its eyes to avoid the sting to sensitive corneas.
The eastern edge of the Great Barrier Reef...
plummets into the depths of the coral sea.
Many deep-water creatures gather on these undersea escarpments.
A chambered nautilus bobs its way toward deeper water.
Its shell contains gas-filled chambers that can withstand tremendous pressure...
and its primitive eye is little more than a pinhole in front of the light-sensitive retina.
Like the coral reef itself...
its strong shell is made of calcium carbonate.
Once, over 2,000 species of nautiloids dominated life under the sea.
But that was long before dinosaurs roamed the planet.
And the climate above and within the ocean has changed many times since.
Today, only 6 species of nautilus haunt the deep sea.
Sudden changes in climate can exterminate species that cannot adapt quickly.
Corals need carbon dioxide to grow...
but we're putting so much of it into our atmosphere...
that it's causing global temperatures to rise.
If sea water gets too warm, coral reefs bleach white and die.
But even more deadly is a new threat called ocean acidification.
Too much carbon dioxide inhibits the formation of calcium carbonate...
the stuff coral reefs are made of, and the shells of the chambered nautilus...
the cuttlebone, and the skeletons of thousands of other species.
Many animals could become extinct.
Coral reefs could begin to dissolve.
As temperatures rise, many species can move south toward cooler waters.
The dwarf minke whale spends its winter in the Great Barrier Reef.
Then in the spring, it heads south to the cold waters of the Southern Ocean.
Cape Catastrophe, South Australia.
In these cold waters lurks an ancient leviathan...
one of the ocean's most magnificent hunters...
the great white shark.
Great whites often reach 17 feet in length.
A shark that large may weigh more than a ton...
and can easily make a single meal out of a 200-pound sea lion.
Sea lions must remain constantly alert.
The world's largest stingrays also hunt here...
searching for crustaceans and mollusks hiding beneath the sand.
The rays often travel with their own entourage...
a squadron of opportunistic fish...
ready to pounce on small animals frightened from their hiding places.
Most of the time, the great white shark will ignore a stingray.
But not always.
Great whites have often been found with foot-long stingray barbs...
embedded in their jaws.
Australian sea lions are among the rarest of marine mammals.
Once hunted relentlessly, now only 10,000 or so remain.
They seem to be the most carefree of creatures.
But as global temperature rise...
the animals living in South Australia have nowhere further south to move.
Each year in these shallow gardens, giant cuttlefish gather for spawning.
They are the largest cuttlefish in the world.
Males sometimes reach more than 3 feet in length.
Giant males confront each other, competing for females...
hiding in the yellow sponge below.
These confrontations seldom result in serious violence.
Instead, males puff themselves up and look as menacing as possible...
then communicate their willingness to fight...
with angry displays of color and pattern.
As the big males compete...
smaller males, called sneakers, disguise themselves as females.
Then, cloaked in feminine charm...
they slip past the dueling giants unchallenged.
Females seem to find the cross-dressing males quite attractive.
Sneakers are surprisingly successful lovers.
Giant cuttlefish mate face to face...
in a tangled embrace that may last many minutes.
The urge to find a mate is strong but this cuttlefish is hungry.
The crab's sharp claws cause the cuttlefish to hesitate.
No one likes to be pinched in the face.
But a crab dinner certainly seems worth it.
A female has deposited her eggs in a crevice beneath the reef.
This is her final act.
In the next few weeks...
all of the adult male and female cuttlefish will die.
Giant cuttlefish live only 2 years.
But these have left their legacy.
In about 4 months, these eggs will hatch...
and a new generation of giants will inherit this undersea garden.
Swarms of mysid shrimp roll over the reef like a mountain fog.
These tiny shrimp become food for many species.
One is among the most bizarre of all ocean creatures.
The weedy sea dragon...
is one of only 3 species of sea dragon that exist on Earth.
He propels himself by undulating tiny transparent fins on his back...
and on either side of his head.
The dragon slurps his dinner with a long tubular snout...
that's perfectly designed for capturing tiny shrimp.
The other dragon living here...
defies even the most fertile imagination.
The leafy sea dragon.
He has turned camouflage into an exquisite work of art.
Sea dragons seldom venture far from home.
Indeed, these delicate creatures are not designed to swim fast or far.
As the climate changes...
undersea gardens in the gulfs of South Australia...
are beginning to die out.
Subtitles: Arigon
When these gardens disappear...
the dragons must vanish with them.
But there are hopeful signs of an even greater change taking place.
It's a change within us.
We finally seem ready to accept the responsibility...
for the changes we are causing to our atmosphere...
our oceans, and our planet.
We have the skills.
If we apply them, our legacy could be an ocean wonderland...
where dragons still roam...
and where sea lions are forever at play.
[ENGLISH SDH]