The Cape of Good Hope, on Africa's southerly tip.
Here, two great seas meet. One, the warm Indian Ocean,
the other, the chilly Atlantic.
And as they mingle, so they create a billowing cloak
that drapes the summit of Table Mountain.
Spectacular though this is, the mountain's cloudy covering
is only a hint of the profound influence
that these two very different oceans have on the fortunes of life here.
And not just here at the Cape,
but across the length and breadth of southern Africa.
Two thousand miles north from the Cape,
beneath this sandy beach, new life is stirring.
Hundreds of baby green turtles
emerge like a torrent from the safety of their nest.
Each one, just seven centimetres long,
must make a hundred-metre sprint down the beach.
From the moment they hatch,
they're driven by an instinctive urge to run to the sea.
Few creatures start life with the odds for success
so heavily stacked against them.
Yellow-billed kites.
Pied crows.
But so many of these hatchlings appear together,
that predators can't catch them all.
Last out, this baby might seem doomed.
But struggling out late could just give her a chance.
The crows seem insatiable.
Even those that reach the sea aren't safe.
This female has to make a dash for it.
She's still in danger, and not just from above.
A ghost crab may be smaller than the hatchling,
but it has the strength to drag her into its lair.
Not this time.
At last, the sea.
She has to catch a breath if she's not to drown,
but the pounding waves make it desperately difficult.
Beyond the surf, calmer water,
but even here, the hatchling is not out of danger.
She dives.
Just in time.
Only one hatchling in a thousand will survive to adulthood,
but if she does, she may live for 80 years.
For now, the ocean is there to be explored.
As the hatchling disappears into the deep blue,
she swims into the waters of one the planet's most powerful currents.
The Agulhas.
The Agulhas sweeps south towards the Cape,
transporting a hundred billion gallons of warm water every day.
These tropical seas are so warm, they evaporate on an enormous scale.
Water vapour rises until, at altitude,
it cools and condenses into clouds.
As the clouds drift inland,
they bring rain to one of the least- explored corners of our planet.
The mountains of Mozambique.
THUNDERCLAP
This the wettest place in southern Africa.
Decades of civil war have kept travellers away
from this little-known land.
It was satellite mapping that revealed the full extent
of the forest that grows here,
so now it's known to outsiders as the Google rainforest.
It could also be called the butterfly forest.
After the rains, butterflies have emerged together in huge numbers.
As soon as their wings dry out, they will take to the air.
Their goal? To find a mate.
But how?
There may be thousands close by, but the foliage is so thick,
it's difficult for them to find each other.
They have a remarkable solution.
They follow rivers upstream and travel to higher ground.
The journey can take hours of determined flying.
Eventually they emerge into the only open space there is.
The treeless peak of Mount Mabu.
Up here, free from the confines of the forest,
they hold a butterfly ball.
Now the butterflies have all the space they need
for their aerobatic courtship.
The male's strategy is simple.
Fly higher and faster than the competition,
and just maybe you'll win a virgin female.
This spectacular gathering, unseen by outsiders until now,
happens for just half an hour each morning
and for just a few weeks in the year.
Once mated, the females descend back to the rainforest to lay their eggs.
A forest that only exists because of moisture rising
from the warm Agulhas current
hundreds of miles away in the Indian Ocean.
The rainwater now flows southwards from Mozambique's highest peaks
to the lowlands of the Eastern Cape.
And where the land flattens, rivers slow,
creating a vast swamp 50 miles across.
This is Gorongosa.
Here, all kinds of creatures come to catch fish.
Whiskered catfish work as a team.
They take a gulp of air at the surface
and then belch it out underwater to create a net of bubbles.
And that traps little fish.
There are fish for everyone.
And each species has its own technique for catching them.
It's all very well having a big beak,
but you've still got to know how to use it.
This young pelican has a lot to learn...
. . and not long to do so.
Maybe, like the catfish, teamwork is the answer.
It's certainly working for the flock,
and this pelican seems to be getting the hang of it.
But surely it can't swallow that catfish?
Trying to was a mistake.
The rainwater, briefly held in Gorongosa's swamp,
has now been enriched with silt and sand.
All down this coast, sediment-laden rivers - the Zambezi, the Limpopo,
the Save - drain back to the sea,
and there they meet the Agulhas current.
And what happens to all that sand?
Over the millennia, the Agulhas has worked it
into a complex underwater landscape.
This vast sand sculpture is the Bazaruto Archipelago,
the oldest of its kind in the world.
It may look like paradise, but living here is not easy.
For 100,000 years, the Agulhas Current has battered
these submerged dunes with underwater sandstorms.
But where the water is deep enough to escape these storms,
nutrients carried from Africa's interior fuel an explosion of life.
A rare oceanic hunter rules here.
Giant Kingfish.
As big as a man, and weight for weight,
one of the most powerful fish in the sea.
Despite their size, they're extraordinarily agile when hunting.
Normally kingfish are solitary,
but for just a few weeks each year, they gather at places
like Bazaruto and prepare for an extraordinary journey.
One that will take them far inland.
The Mtentu River.
A king of kingfish leads them upstream.
As they travel further into fresh water,
they seem to change from aggressive hunters into dedicated pilgrims.
Now, many miles from their natural home,
and in response to an unknown cue, they stop and begin to circle.
Other marine fish that migrate upriver usually do so in order
to breed, but there's no evidence that these kingfish spawn up here.
Neither do they hunt. So what are they doing?
In truth, the purpose of this strange behaviour is still unknown.
Within a few weeks,
they will retrace their journey back to the ocean.
The lives of kingfish, like those of turtles and butterflies
and pelicans, are influenced by the Agulhas Current.
But that influence can only reach so far.
And this is why.
The Drakensberg mountains.
Here, local people say that the vultures soar so high,
they can see into the future.
These sheer cliffs, rising to over 3,000 metres,
hold back the advancing rain clouds
and, as a result, the land beyond them is starved of water.
This is the greatest expanse of sand in the world.
A seemingly-endless desert
that is the vast parched centre of Southern Africa.
Thousands of miles to the west,
where this desert meets the Atlantic Ocean, another current prevails.
But the Benguela Current, surging up the west side of Africa,
has a very different character.
It's extremely cold, full of nutrients
and it's thronged with life.
A great white shark.
They can raise their body temperature to 10 degrees
above that of the surrounding sea.
But doing so requires an enormous amount of high-grade fuel.
So this is a great bonanza for them - the body of a dead whale.
The carcass will draw in every great white for miles around.
And here, off Cape Town, that means a lot of sharks.
Instead of feeding in a frenzy,
these sharks have rather refined table manners.
They swim side-by-side to get the measure of each other.
Then each takes its turn.
This female is the biggest, so she eats first.
The next only feeds when she gives way.
The waters of the Benguela are so rich,
they support more great white sharks than any other seas on the planet.
And they are so cold,
they attract some surprising creatures to these African shores.
Penguins.
African penguins.
This female is returning to relieve her partner.
Of course there's no ice here,
but these rocks can be almost as slippery.
But there are more serious obstacles
than the slippery rocks awaiting them.
It's his turn to feed, so he leaves her to look after their eggs.
Now she must tackle a problem faced by no other kind of penguin.
For the next 10 days, she must protect her eggs
from the African sun.
A dense coat of feathers
that keeps her warm in cold seas now stifles her.
On these exposed rocks,
she must shade her eggs instead of keeping them warm.
Everything here seems the wrong way round.
For some, the soaring temperature is too much.
A neighbour deserts his nest.
His egg will not survive.
He's not the only one to give up.
Some years, not a single chick is reared.
Penguins are adapted
to withstand temperatures of 40 degrees below zero,
not 40 degrees above.
Now, at the hottest part of the day, the very worst time,
her chicks are hatching.
Just when they need her most, she's reaching the limit of her endurance.
After 10 days of intensive fishing,
the chicks' father comes back to take his turn at the nest.
But will he be too late?
He greets his young for the very first time.
The coolness of the Benguela Current brought the penguins here
but that very coolness is a great disadvantage,
because it generates little rain.
It can, however, produce moisture in a different form.
A thick blanket of fog rolls in from the sea
and condenses on this thirsty land.
And each year, the desert bursts into life with a dazzling display.
Water is so scarce that this show will not last long,
so plants compete to attract their pollinators with colour.
Here in Namaqualand, a 600-mile strip of coastal desert
becomes carpeted with blooms.
The morning sun opens a Namaqua daisy,
and reveals a male monkey beetle asleep inside.
Nights here are so cold that monkey beetles shelter within
the closed-up petals of the daisies.
The habit brings benefits to both sides.
The beetle is kept warm and the flower gets pollinated.
But now the beetle has urgent business. He must find a mate.
As he searches, he hops from bloom to bloom, pollinating each in turn.
At last he spots a potential mate.
A golden princess.
But here comes trouble.
A rival.
There's no time for introductions.
But he's been too slow.
The rivals immediately begin to brawl.
The female will only mate inside the daisy,
so they wrestle for possession.
They're so engrossed in fighting, they've pushed her off.
The challenger is ejected.
The winner wastes no time before getting back to business.
At last!
Now there will be a new generation of monkey beetles
to pollinate these Namaqualand flowers.
For most of the year this land is desperately dry,
but just occasionally,
brief, violent storms sweep in from the cold ocean.
Springbok have been roaming this desert for many months,
searching for one of these rare and highly localised downpours.
The grass is sprouting.
And that is worth celebrating!
If you're a springbok, that means pronking.
MUSIC: "Waltz of the Flowers" by Tchaikovsky
We still don't know exactly why they do this.
The simplest answer is that they're dancing for joy.
Africa's most southerly tip.
This is where the two great ocean currents, the warm Agulhas
and the cold Benguela, crash into one another.
And this collision, in itself, draws in life in abundance.
A super-pod of hunting dolphins, 5,000 strong.
And shadowing them...
. . Africa's biggest predator.
A Bryde's whale.
This female is 15 metres long
and weighs more than a whole family of elephants.
The dolphins are in pursuit of sardines -
millions of them.
But these cold-water fish are heading towards an impenetrable
barrier of warm water that they will not cross, the Agulhas Current.
They're trapped.
And that gives the whale her chance.
But the sardines are so speedy
that the whale only catches a few with each pass.
More and more hunters arrive.
The whale needs the other hunters to push the fish upwards,
forcing them against the surface.
Now they have nowhere to escape.
With each lumbering turn she loses precious time,
time that favours the more nimble.
The Bryde's whale probably knows
that this opportunity will last less than five minutes.
And with the last few lunges, she finally cashes in.
The forces that triggered this great event
have also shaped the fortunes of life
far beyond this particular battleground.
Without these currents, Southern Africa would be a desert.
But combined, the very different powers of the Agulhas
and the Benguela have transformed the Cape
into a land where life can flourish.
The Comoro Islands off Africa's east coast
are a haven for green turtles.
Every year, a million turtles hatch on these beaches,
but the chances of any one of them surviving is tiny.
The Africa team came here to try and capture the dramatic
first few minutes in the lives of these baby turtles.
It was to be both a technical, and surprisingly emotional challenge.
It's only when you get down on the eye level of the baby turtle
that you realise what an enormous journey it's got to make
down over the beach, and it really is quite epic.
That's fine. Oh, yeah, that's lovely.
It's using all these complicated, heavy bits of equipment
which hopefully will enable us
to get into the world of a turtle which is just a few inches long.
As they break out of all the soft sand, they hit the hard sand
and that's where the real sprint takes place.
They must be desperate to hit that water,
because you can see the sea's just over the horizon.
We're following them all the way down
and you do kind of get involved with them and cheering them on.
OK, slow down a bit. Slow down.
And suddenly all these crows come flocking in
and start picking them off and you just think, that's just so unfair.
Lots more coming in. Just loads coming in now.
I do, God, I feel for them.
You know it's really quite upsetting
and particularly when you're looking through the camera
and I'm just filling frame with a turtle running down the beach,
then suddenly from nowhere, a beak comes in and whoosh, that's it.
That turtle's no more.
The turtles that escape the perils of the beach
still have to face pounding surf.
But, at last, they're in their element.
More than can be said for the crew.
They're faster than you, aren't they? Yep.
It's a bit embarrassing.
Beaten by something that's less than a day old.
When you see hatchlings get off the beach
and going in the white water, you'd think they'd just get obliterated.
They just punch through the water - they do get flung around
but then they just right themselves, keep on swimming and they're
ahead of you, coming out the back of the wave and it's amazing.
You're seeing all these baby turtles getting picked off,
left, right and centre, but they just keep going.
They are just so resilient.
And that made what happened next so distressing.
A particularly high spring tide flooded the beach.
Any baby turtles still in their nests would be lucky to survive.
See it bubbling out as well. Yeah. See the air.
Well, it means that basically anything below
that line's going to be gone.
Let's hope and pray it's not, but...
As you say, we don't know, let's wait and see.
All across the world, turtles are in decline.
Their eggs are stolen,
the adults are hunted for their flesh
and they drown in fishing nets.
But here in the Comoros, they have friends.
It's amazing here in Itsamia.
It's just a really heartening story of how the local people
are doing everything they can to protect sort of
what they think of as their turtles.
And some of the baby turtles have survived the flood tide.
The whole village comes to help the hatchlings.
But the most important effort is to protect
the adults from outsiders who would hunt them for their meat.
They've taken it upon themselves to really police the beaches
around here and make sure that poaching is kept to a minimum.
The selfless protection these people provide means that this is
one of the few places in the world where turtle numbers
are actually increasing.
And remarkably, here in Itsamia, the population has in fact
doubled in the last decade.
As the shoot was coming to the end,
cameraman Kevin Flay noticed that some of the turtles
that made it through the surf faced one last danger.
I'm getting shots of a kite which is flying down
and taking turtles off the water surface.
That was a part of the story we had to tell.
The aim is for us to be underwater,
looking straight up as this happens,
and that's actually really quite hard.
OK. Three, two, one...
Undeterred, the crew got into position.
There we go, the kite's up.
You can't see where you're going because my head's glued
to this viewfinder, so I'm banging into rocks and things like that.
I'm really just trying to keep the turtle in shot.
Something came in then.
She came in and swooped down over the water's surface.
And you could see the kite from underwater?
I could see it, I could see the shape.
In frame and you were running? Yep.
Didn't take the turtle. Didn't take the turtle.
Probably that's the best of both worlds, because we got
our lovely underwater shot of a kite and the turtle gets away!
This lucky hatchling isn't the only one.
With the help of the village of Itsamia, thousands more
have a chance to make it to the open ocean.
It's only really local populations that can actually support
and sustain this conservation work.
If it comes from the roots upwards, then it's got a chance of success.
You know, I think it's amazing, I really do, the fact that they
do this and you know we should see it more often around the world.
It's hard not to admire these extraordinary little creatures
as they battle against such odds.
This baby turtle won't touch land again
until she returns to the very same island to lay her own eggs.
With luck, she'll find the beach is still protected
by the people of Itsamia.
Next time, the vast cauldron of the Sahara Desert.
This colossal wilderness
covers one-third of the entire African continent.
To survive here, life is stretched to its very limits.
Simply being tough isn't enough.
Only the most extraordinary creatures will triumph.
Subtitles by Red Bee Media Ltd