Nearly three quarters of our planet lies underwater.
Now, venture beneath the waves, and enter an astonishing world.
It's a world where even rock is alive.
Amazing animals live, hide, and hunt on the coral reef.
This is the kingdom of the oceans.
***** subs by HC *****
Night on the reef. The streets are dark.
Most of residents are asleep, or hiding.
They are wise to stay indoors tonight, because predators are on the prowl.
It's a gang of whitetip reef sharks looking for action.
Anything that moves is fair game.
As they scour the reef, it's every shark for himself, ...
but if one shark corners a victim, they all pile on.
This little fish seems to be in the wrong place at the wrong time.
The best way to survive around these killers is to avoid being noticed.
Camouflage is recommended.
Whitetip reef sharks make the most of this hunting ground.
It's a landscape built, not of stone and sand, but of coral.
For at least 25 million years,
coral reefs have been home to some of the ocean's richest wildlife communities.
Evolution has produced a dazzling array of forms and colours.
It's the marine equivalent of a rainforest.
The most amazing creature here may be the coral, itself.
This moray eel swims through a garden
composed, not of plants, but of tiny animals.
Coral looks like rock, but it's alive, and it comes in myriad shapes and sizes.
And, it reproduces in an unusual way.
For many corals, it happens once a year, at night - always at night -
just after the full moon.
All at once, the entire reef unleashes a blizzard of eggs and sperm.
It's one of nature's greatest spectacles,
but it was never seen by scientists until 1981.
These eggs and sperm emerge from coral polyps;
individual animals that fuse together to form the living reef.
The tiny travellers are set free to ride the tides,
and, somehow, to find each other.
Those that succeed and survive
plant themselves on some distant surface and grow into adult polyps.
Joining with others of their kind, they begin a new coral colony.
The process repeats itself innumerable times,
layer upon layer, year after year,
As each new generation builds upon the skeleton of its ancestors,
the colony expands in every direction...
and a coral reef is born.
Coral reefs can stretch for hundreds of kilometres.
The largest of all, Australia's Great Barrier reef,
is so vast, it's the only living thing on Earth
visible with the naked eye from outer space.
Entire island chains can be made from coral.
More than any other creature on Earth,
coral crosses the boundary between living things and geology.
As oceans rise and fall, and continents collide,
ancient coral reefs end up deep inside Earth's highest peaks.
Underwater, new coral grows on old reefs.
Sponges and sea fans thrive here.
If conditions are right, young coral can spread far afield,
and gain a foothold in surprising new locations.
It creates a thriving habitat, where once there was bare rock.
Schools of fish are welcome on the new reef.
Moorish idols peck at the coral, and nibble on the seaweed and sponges.
Parrot fish consume coral, too.
It's not really the coral they're after, though.
It's algae, that live inside the polyps.
These fish gather on the reef in large numbers.
Their constant grazing can change the very shape of the reef.
The reef grows slowly.
The fish flourish here,
so they stick around, no matter what.
Even as the roiling tide batters the reef, they take it in stride.
When darkness falls, things begin to settle down.
Fish that spent the day feeding look for safe places to sleep.
They curl up in coral crevices, ...
or nestle in the embrace of coral branches.
Security is more important than comfort,
because a sleeping fish is defenceless against the predators of the night.
A whole new cast of characters wanders the reef after dark.
Crustaceans spend the day hiding in the shallows,
but nighttime is their time to flourish.
They're not too particular about their diet.
Any small creature will do, living or dead.
It's all the same to them.
While they hunt, they must avoid becoming prey.
Some hermit crabs defend themselves with borrowed weapons.
They attach small anemones to their shells.
The anemones are very much alive, and extremely venomous.
Even the coral itself is at risk of attack.
The spiny crown-of-thorns starfish has a taste for live coral polyps, ...
but, as it munches on the reef, it's being munched,
by a big Triton's Trumpet sea snail,
The sea snail ignores the starfish's venomous thorns,
and, slowly, relentlessly, devours it.
Effective reef predators choose their prey wisely.
The giant moray eel has poor eyesight,
but a keen sense of smell, and a mouth full of sharp teeth.
But, even a giant moray must be cautious.
A lion fish, with its arsenal of venomous spines,
is not a good choice for dinner.
Once the moray sniffs out the problem, he thinks better of the idea.
Getting around, and getting away from trouble.
Both are essential for reef residents.
This sea slug has options. It can crawl...
or, it can fly.
It earned the name "Spanish Dancer" from its red mantle,
and elaborate choreography.
Of course, to the Spanish Dancer, this isn't a dance.
This is just how it makes its way through the world.
Another flashy dresser is the ribbon moray.
Normally, it's a reclusive fish,
but when it steps out, it knows how to move.
Just after dawn, a pack of leather bass hunts together.
They're voracious feeders,
but bigger predators always have the right of way.
Determined foragers, they search every nook and cranny.
But, desperate little fish seek refuge in the needles of a sea urchin.
Even that doesn't deter the bass.
They'll just wait for their chance to strike.
At first glance, it seems like a trumpet fish
would have a hard time hunting on the reef.
It can't swim very fast; A skinny guy, without much brawn.
But the trumpet fish has some tricks which give it an edge.
It can change colour and pattern to blend into its background.
And, the way it swims makes it almost invisible to prey:
Slow, rigid; nearly motionless in the water.
It looks more like a floating stick than a threatening predator.
When it's still, this peacock flounder is nearly impossible to spot.
When it moves, it maintains a low profile:
swimming on one side and hugging the bottom.
A young flounder has one eye on each side of its body,
but as it grows older, the right eye migrates to the left side,
so it can look at something other than the sea floor.
On a healthy reef, both predators and prey abound.
Coral reefs are hotspots of ocean diversity.
Home to a quarter of all marine species.
Life on the reef comes in all sizes.
The water is rich in microscopic plankton,
and that attracts hungry giants,
like a 2-ton Pacific manta, with its 8-metre wingspan.
When you're this big, feeding is serious business,
but the manta makes it look easy.
This graceful manoeuvre may be a way for the manta to corral its prey.
Flying in lazy loops, the manta just opens it mouth,
and the plankton pour in.
For a manta ray, the reef is a land of plenty,
but it doesn't come here just to eat.
While they visit the reef, the manta ray, and the remoras that ride along with it,
take advantage of the local cleaning service.
It's extremely popular.
Clarion angelfish are skilled at picking off dead skin and parasites.
They set up cleaning stations on the reef, and they're in high demand.
If the angelfish are booked up,
butterfly fish can handle the overflow.
They're sought out by many different species.
From the yellowtail grunt,
to hammerhead sharks.
It seems, there's more to life on the reef than hunting and hiding.
Interspecies cooperation is surprisingly common.
This cleaning station is well-marked by a giant potato coral.
Sweetlips gather here to be groomed by striped cleaner wrasse.
To make the system work, there has to be a high level of trust.
This potato cod prefers a more discrete setting:
under a coral shelf.
This cod eats a lot small fish everyday,
but the cleaner wrasse are in no danger.
He needs them to take care of his teeth and gills.
Stretching up to 2 metres long, and weighing 100 kilograms,
the potato cod cuts an impressive figure,
but, no fish has a bigger impact on the reef than the humphead parrotfish.
They feed in big schools,
and they have an insatiable appetite for living coral.
Their front teeth are fused into a kind of beak,
which they use for scraping algae, and biting off chunks of coral.
Teeth at the back of the throat grind down the stony coral into a paste.
Anything the parrotfish can't digest is released into the water as fine sand.
An adult humphead parrotfish consumes 5 or 6 tons of coral every year.
That can change the shape of the reef,
and produce a lot of sand.
Some of this sand ends up carpeting the bottoms of tropical lagoons.
These peaceful oases are framed by walls of coral
that hold back the churning sea.
With the currents blocked, and the tide tamed,
a lagoon is a sanctuary in mid-ocean.
It's the perfect spot for deep-sea travellers to stop and rest.
A humpback whale has chosen this lagoon to give birth.
Her calf was born a giant:
Four and half metres long, and weighing three quarters of a ton.
But, like most infant mammals, he's dependent on his mother,
and he won't stray far from her side.
Without her protection, the calf could fall prey to killer whales.
The safety of a tropical lagoon is a good place for the calf to begin life.
He has to surface to breathe much more often than his mother,
and until he develops a layer of blubber, he can't float very well.
She's usually just beneath him, to guard against attack from below.
Theirs is a remarkable bond.
They'll stay in this lagoon for weeks,
to give the calf a chance to grow stronger and much bigger.
Then, together, they'll begin a long journey to their summer feeding grounds.
In the meantime, they won't be alone.
Other marine mammals have discovered the lagoon, too.
Here, in this refuge,
it's quiet enough for spinner dolphins to carry on long clicking conversations.
And, it's ideal for other kinds of interaction, too. Like sex.
Among dolphins, sex is not reserved for reproduction.
It's, just, part of being sociable,
and it's not always a simple one-on-one affair.
Sometimes, it takes three to tango, or even more.
Courtship for these cod is more intimate than it is among dolphins.
They perform a delicate dance, just for two.
In the ocean, mating is a game with endless variations.
Some partnerships are long-lasting,
but more often, they're merely brief encounters.
Or, mating can be a group effort; a, kind of, reproductive flash mob.
They cast the fate of the next generation to the currents.
A bush of coral serves as a more secure nest
for the eggs of a broadclub cuttlefish.
The eggs harden after they're laid,
which makes it almost impossible
for predators to extract them from the coral.
Though cuttlefish aren't, exactly, doting parents,
they do their best to give their young ones a good start in life.
But, these cuttlefish have other, more impressive talents.
They're expert hunters.
They're, also, master illusionists,
able to control the colour and pattern of their skin at will.
It's a gift they use to dazzle their prey.
They even practice the dark art of hypnosis.
Many creatures of the reef take on disguises, in order to survive.
The decorator crab adorns it shell with bits of seaweed and fragments of sponge.
An octopus can alter texture and colour to blend into its surroundings.
Few reef dwellers can top the stonefish, when it comes to camouflage.
It's a perfect match for the coral background.
Invisible, until it moves.
But, there are times when hiding, just, doesn't seem that necessary.
The gang of whitetip reef sharks beds down together during the day.
Even when it rests, a shark's eyes stay open.
Unlike many sharks, whitetips don't have to keep swimming, in order to breathe,...
so, they can enjoy some downtime,
and recover from their bouts of high-energy hunting.
Nearby, fish engage in, what appears to be, an odd ritual.
They take turns rubbing themselves on a rock.
With the sharks so close, it looks like a dangerous stunt,
but it may be another way to get rid of scales and parasites.
They'll use any rough surface that's handy,
like a passing turtle...
or a shark. Even one that's wide awake.
This behaviour - fish rubbing against a shark's skin -
was, only, recently documented.
It's more proof that here on the reef, good grooming matters.
Life on the reef can seem idyllic,
but that doesn't prevent some creatures from taking a road trip.
A formation of blotched fantail rays strikes out for parts unknown.
The rays cross flat, sandy plains free of coral
They seek a world beyond the next ridge.
It's a good bet; there are always more wonders out there.
A wobbegong shark is on its own voyage of discovery.
It arrives at a place where a human tragedy
created a different kind of reef.
In March, 1911, the SS Yongala went down off the Australian coast,
with 122 passengers and crew.
The ship was lost until 1958.
During that span of nearly a half a century,
coral took root on the Yongala's steel skeleton.
Fish and other sea creatures followed, to make their home here, too.
Today, what's left of the ship is a thriving reef,
protected and treasured.
It bridges the gap between the human world, and the wild one.
***** subs by HC *****