The oceans seemingly limitless,
invoke in us a sense of awe and wonder and also sometimes fear.
They cover 70% of the surface of our planet,
and yet they are still the least explored.
Hidden beneath the waves right beneath my feet,
there are creatures beyond our imagination.
With revolutionary technology, we can enter new worlds...
And shine the light on behaviours
in ways that were impossible just a generation ago.
We've also recognized an uncomfortable fact.
The health of our ocean is under threat.
They're changing at a faster rate
than ever before in human history.
Never has there been a more crucial time
to reveal what is going on beneath the surface of the seas.
In this first episode,
we will journey across the globe
from the warm waters of the tropics
to the coldest around the poles.
To bring us a new understanding of live beneath the waves.
This is Blue Planet II.
The surface of the ocean
conceals the many creatures that live beneath.
But not all.
Bottlenose dolphins.
They're extremely intelligent.
And with this intelligence comes playfulness.
They surf.
And as far as we can tell, they do so for the sheer joy of it.
But to properly appreciate their true character,
you have to travel with them into their world.
A pod of bottlenose dolphins
is visiting a coral reef in the Red Sea.
For the youngsters, there are things to be learned here.
The adults lead a calf to a particular bush-like coral
called a Gorgonian.
And here, the adults behave rather strangely.
They deliberately rub themselves through the fronds.
Their calf seems reluctant to do so.
By watching his elders,
he may be realizing that this is something he ought to do.
Gorgonia fronds, in fact, are covered with a mucous
that can have anti-inflammatory and antimicrobial properties.
So maybe the adult dolphins are doing this
to protect themselves from infection.
The dolphins' intimate knowledge of the reef
is spurring us to search for new medicines here, too.
Tropical coral reefs
occupy only a tenth of one percent of the ocean floor.
But their shallow warm waters and stable year round conditions,
support some of the most crowded and varied communities
to be found anywhere in the oceans.
And there are new discoveries to be made on every one of them.
One creature on Australia's Great Barrier Reef
is challenging our understanding of fish intelligence.
A tusk fish.
And you can see why it gets its name.
He does something few would have believed a fish could do.
Every morning, he travels to the edge of the reef.
He's searching for something special to eat
amongst the coral rubble and sand.
Here's one.
A small clam.
But how to crack it open and get to the meat?
He takes it all the way back
to his special kitchen.
A bowl-shaped coral
that has a particular bump on the inside that he always uses.
It's not easy if you have no hands.
Whoops.
There he goes again.
But he's got great determination
and surprising accuracy.
At last.
So here is a fish that uses tools.
Some fish are much cleverer than you might suppose.
The density of the animals on tropical reefs
makes competition inevitable and extreme.
Not only for those that lived within the reef,
but for the birds that fly above them.
During the dry season,
over half a million terns
crowd onto this remote atoll in the Indian Ocean.
Their chicks are still in their dark, juvenile plumage.
They vary in age.
Whilst the more advanced chicks take to the air,
others aren't quite ready yet.
Those just starting to learn to fly
use the shallow lagoon that occupies the centre of the atoll
as their training ground.
It's difficult for some of them to stay aloft for long.
Giant trevallies.
Usually, they're solitary hunters,
but about 50 of them have come here from neighbouring reefs
attracted by this abundance of potential prey.
The fledglings stay out of the water if they can,
they even drink on the wing.
If the trevally are to catch one now,
they have to up their game.
So there is a fish here that amazingly
has a brain capable of calculating the airspeed,
altitude and trajectory of a bird.
The time comes when every fledgling has to take to the air
and collect food for itself.
Their parents lead them to the training grounds.
If they're to survive,
they must learn quickly.
After a month of practising over the lagoon,
the youngsters start to leave
and take their chances out over the open sea.
The oceans hold 97% of all the water in the world.
As the sun warms their surface, water evaporates.
The vapour rises into the sky
until it cools and condenses into towering clouds.
And they generate huge storms.
The spin of the earth deflects these storms
north and south into cooler latitudes.
As they travel across the sea,
storm-driven winds create huge swells.
When the swells reach shallower waters,
they rise into gigantic waves.
In its lifetime, a large storm can release energy
that is the equivalent of 10,000 nuclear bombs.
These are the seasonal seas.
And when they warm in spring,
they can suddenly explode with life.
Mobula rays have gathered in Mexico's Sea of Cortez in vast numbers.
Why do they leap?
Is it to tell others that they're here?
No one knows.