Original subtitles

A great current rises slowly from the abyss

into the middle of the world's largest ocean,

where it soothes an exhausted humpback whale

who has just become a mother.

She's traveled across 3,000 miles of open ocean to give birth...

...in these calm, tropical waters.

Humpbacks are intelligent and sensitive.

Here, they have the peace and time they need

to establish the vital mother-calf bond.

A hug helps affirm one of nature's strongest connections.

But they can't stay here.

If they get hit by a storm in the open ocean,

it could separate them.

So, they're swimming for the only shelter in this part of the Central Pacific,

the islands of Hawai'i.

Getting there is dangerous.

Male humpbacks patrol the island's approaches...

...knowing that every adult female coming here will soon be ready to breed,

and worth the chase.

Her two-ton newborn is unaware of the dangers.

But babies can be killed or separated in the crush of 40-ton males.

So, Mom communicates in a whisper, trying not to be overheard.

Protecting her son is her priority.

But he wants to play.

His innocent splashes give them away.

Now, the race is on.

They accelerate to 15 miles an hour.

A dozen rivals start competing for her

in a heat run.

With her calf in tow, Mom can't outrun them.

She's caught.

And all she can do now is try to protect her calf

as the males fight to be by her side.

Eighty tons of blubber and muscle collide.

Mom uses her 15-foot-long pectoral fin to fend off a male who gets too close.

She does everything she can to shield her baby.

He's tiring fast.

But shallow water is ahead.

Then, the biggest male closes in again

and releases a barrier of bubbles.

It's a display of dominance,

showing that he's got energy to spare.

Forcing away any rival that comes too close.

Giving Mom and calf the chance to dive out of sight.

She allows him to escort them both to safety.

With his protection, they can rest.

And if he's patient enough, she may, in time, choose to mate with him.

But her calf remains her top priority.

Now, he can suckle in peace...

and safely play...

splashing around as much as he wants.

In just a few months, Mom and her calf,

along with the rest of Hawai'i's humpbacks,

will begin their trek north

to their rich summer feeding grounds,

half an ocean away.

Our oceans are so vast that they define the color of our planet.

Throughout human history, they've been a gateway to the unknown.

Even today, the surface of the ocean is a portal to another world.

One of mystery...

and drama...

populated by creatures so intelligent

and rarely seen

that we are only just beginning to get to know them.

But as the world goes through unprecedented change...

so too do our oceans.

We'll witness incredible ways to survive...

...as we face this fast-changing world together.

We'll experience their challenges...

...reveal their secrets,

and discover lives more like ours...

...than we could have ever imagined.

Never has there been a more important time for us to explore the wonders...

surprises...

and joys of life across our oceans.

Our voyage begins in the expanse of blue that covers almost a third of our planet.

Of all our oceans, the Pacific is the largest and the deepest.

Many currents swirl around this mighty ocean,

but one unites them all.

It's part of the most powerful circulation of water on Earth.

We call it the global ocean current...

and it brings the Pacific to life in astonishing ways.

Like on the reefs of the West Pacific,

where it helps support

the greatest variety of sea life found anywhere.

It's home to the world's most famous fish.

A clownfish.

And his family.

They live in an anemone beside the drop-off,

with ocean views.

The great current refreshes the corals that built this world...

allowing them to thrive...

by bringing clean, oxygenated water

from the open ocean right to their doorstep.

Just what this little guy needs.

Because soon, he'll become a first-time parent.

Mom has laid over 100 precious eggs, and it's now Dad's job to look after them.

Which means keeping them tidy...

...brushing away dirt and sand...

and providing round-the-clock care.

The reef is full of predators...

and a well-tended anemone will protect the family with its stinging tentacles...

providing Dad does his chores...

and keeps everything spic and span.

But staying on top of the housework

and keeping the eggs clean is a tall order.

Especially today.

A raft of floating stones.

It's a sign of elemental forces at work.

Because somewhere far away,

an undersea volcano has erupted,

creating pumice...

billions of gas-filled volcanic rocks,

which can be carried for thousands of miles

on the global ocean current.

It's a new dad's worst nightmare.

But in the long term,

this mess could actually be good news for the whole neighborhood.

Because pumice will slowly dissolve,

releasing nutrients that support development and growth.

Turns out, a little dirt really doesn't hurt.

Wherever it flows, the great current delivers extraordinary riches,

and in the Pacific, its path is guided by a colossal force.

One with the power to make mountains.

A 25,000-mile chain of active volcanoes, known as the Ring of Fire,

surrounds this ocean.

From the West Pacific, they form a mountainous coastline

that guides the great current on a loop northwards,

carrying over 50 million tons of tropical water every second

towards the islands of Japan...

...where it warms the surrounding water to 80 degrees Fahrenheit.

Just enough to sustain tropical coral reefs

further north than anywhere else on Earth.

A young broad club cuttlefish...

is looking for romance.

Because today marks the start of the annual Cuttlefish Ball,

held each spring when the warming water helps trigger their urge to find a mate.

Cuttlefish have the astonishing ability

to communicate their feelings through their skin.

But this superpower can also be a weakness.

Especially if you're a little anxious about your first date.

One particular female has caught his eye.

Deep breath.

Here goes.

As he approaches,

his brain connects directly with thousands of pixels in his skin,

to say,

"Hi. I'm cool, calm and relaxed."

Just what she is looking for.

But here comes trouble.

These tough guys are making their aggression clear.

Their swagger and zebra stripes mean they're angry...

...and not afraid to throw their weight around.

The young male is cut out.

But like Hulk, they shouldn't make him angry.

They won't like him when he's angry.

Instantly he displays his own intense zebra stripes.

With his temper unleashed...

he scares off a rival.

And he returns to the female.

But she's not interested in a tough guy.

To win her over, he'll need to keep his cool.

So, in an incredible display,

he appears to split his personality.

With his relaxed tones, he shows the female he's calm,

while showing his rivals his macho stripes.

At last, with a little anger management, his superpower has become an advantage.

Showing he's the strong yet sensitive type.

And finally, she's impressed.

Things move fast in the cuttlefish world.

And in no time, they're starting a family.

She lays their eggs

where they'll be kept warm and oxygenated by the current.

From here, the great current also transforms its character,

becoming rich with minerals as it passes the active volcanoes

that mark the northern boundary of the Ring of Fire.

So that when it arrives off Alaska three years later...

...it helps fuel an annual feast.

Humpbacks.

They've traveled all the way from Hawai'i in anticipation of this seasonal bounty.

But the fishing isn't what it used to be.

Because these days, our fishing fleets often get there first.

Our appetite for fish means

that marine predators must compete with us.

But these two shady characters have a secret spot.

And a plan...

to outsmart the humans.

By stealing fish...

...from a salmon hatchery.

These nets contain 14 million young salmon

that will soon be released to help repopulate the wild.

Why go up against the fishing fleets when you've got an all-you-can-eat buffet?

But it's a fisheries Fort Knox.

You can't sneak past security when you're 50 feet long.

Unlike some petty thieves.

It seems like an impossible mission.

But this crafty duo have been scoping the joint for years.

And they've got a plan...

to strike the moment the hatchery releases the young salmon.

Step one, get your timing right

and keep a low profile.

With the coast seemingly clear,

the vault is unlocked.

The sound of chains is like a dinner bell...

alerting the whales that the prize is on the move.

Step two, break in before the young salmon get out.

It's a smash-and-grab job...

...but most of the fish break free and start scattering out to sea.

So, the final step is to blow a net of bubbles...

...which conceals a new feeding trick...

using their pectoral fins to herd the fish into an even tighter ball.

These criminal masterminds have pulled off the perfect heist...

although enough salmon do escape to boost numbers in the wild.

In the end, there's nothing the humans can do...

...to stop the ocean's 40-ton thieves.

As it begins to follow the coastline south,

the cold, fertile current enriches the volcanic west coast of North America...

supporting forests of giant kelp,

some towering 180 feet above the seabed...

home to an astonishing variety of life.

Every level is inhabited.

Sea lions soar through the branches.

Sea otters rest in the canopy...

and feed on the forest floor,

which shelters an enchanting world of invertebrates.

The current's influence even transforms life beyond the ocean.

It sustains thousands of miles of coastal rainforest,

including the tallest trees on Earth.

They can only grow here, where the current chills the air,

bathing them in sea mist and delivering soft rain...

...helping keep this entire coastline cool.

When the current reaches Los Angeles,

it slows,

and on a few calm summer days,

the surface layer warms just enough...

to set the stage for a great spectacle.

This incredible light is called bioluminescence,

the glow of billions of microscopic plankton.

As each one is disturbed, it emits a glimmer.

And it's what these California sea lions have been waiting for.

As shoals of sardines feed on the plankton,

they light up...

turning the spotlight on themselves.

All this activity draws dolphins to the feast.

The natural fireworks create so much light that even daytime predators are drawn in.

Who'd have thought?

One of nature's greatest light shows,

hiding in plain sight,

just beyond the bright lights of LA.

As the great current flows toward the tropics,

some diverts into a desert sea.

Mexico's Gulf of California.

By constantly replenishing its waters,

the current helps keep the Gulf fertile and cool.

It's been called the world's aquarium...

for the sheer diversity of fish.

But not all fish are content to hang with a crowd.

Beneath the shoals,

there is a miniature world that's providing a more private venue.

This female signal blenny is on the lookout for a partner.

Several two-inch-long males are keen to compete for her attention.

But she's only interested in the fittest...

largest...

and best-dressed.

So, what better way to choose...

...than to host a dance-off...

and see who has the best rhythm...

style

and stamina.

Each blenny adds their own dance moves,

trying to outdo each other.

Great extension.

Smooth move.

But what's the verdict?

Do the fish have talent?

Hmm.

It's a "no" from her.

But there's no need for murder on the dance floor.

Here's another female.

The party can go on all day...

here in Mexico's most exclusive ballroom.

The global ocean current powers away from the Americas

and into the Central Pacific.

In this wilderness,

voyagers need to cover huge distances to find food.

And where they can, they travel with the current.

Like these spinner dolphins.

It would be easy to lose each other out here.

So, they perform pirouettes up to ten feet in the air.

The noisy splashes help keep them together.

So, they can cruise in super pods up to 5,000 strong.

Out here, far beneath the waves,

the Ring of Fire gives birth to undersea volcanoes and deep-sea vents...

that change the structure of the seabed itself...

with consequences for those swimming far above.

A manta ray hitching a ride with the current.

Her 26-foot wingspan allows her to travel the ocean with ease.

She's heading for a secret rendezvous in the big blue.

A seamount rising from the abyss.

One of over 30,000 peaks hidden beneath the surface of the Pacific.

Built from lava, each one has a unique magnetic signature

from the earth's metals hidden within...

which she can detect using a sense she shares with her relatives.

Sharks.

This allows seamounts to become a meeting place.

And a rare opportunity for solitary ocean wanderers to socialize.

But humans have exploited many of these seamounts...

and fished them out.

In the past 50 years,

the number of sharks have declined by 90% in some parts of the Pacific,

breaking fragile webs of life.

Only by protecting these seamounts

can we glimpse how they enrich life across the Central Pacific.

Reminding us how abundant our oceans can be

when we choose to safeguard them.

Three-quarters of the world's volcanic activity remains submerged.

But every few years, volcanoes break the surface...

...creating new islands as lava escapes from the earth's crust.

When lava flows into the sea, it cools rapidly, building jagged coasts.

Six hundred miles off Ecuador,

a chain of volcanic islands that has risen in the path of the global ocean current.

The Galápagos.

The island's active volcanoes create an intricate shoreline...

and an opportunity for a trailblazing predator.

The Galápagos sea lion...

...and his family.

Their pup is still too young to catch her own food.

So, it's up to Mom and Dad...

to do the hunting.

They've chosen to make their home on these harsh volcanic rocks

for a good reason.

It's protected from the open ocean by a maze of gullies and shallow bays.

And yet, they can also reach

some of the most abundant fish-filled seas in the Central Pacific.

As the great current collides with these volcanic islands,

it forces food-rich water up...

...fertilizing the surface...

and fueling an explosion of life just offshore.

But for the sea lions,

bringing any of this back to the youngster won't be easy.

Because they have got competition.

Blacktips.

The upwelling attracts yellowfin tuna, one of the fastest fish in the sea...

...reaching speeds of 40 miles an hour.

There's no way the sea lions could catch them out here.

Tuna normally avoid shallow water.

So, the bull blows a wall of bullets,

which cuts off their escape and forces them towards the shore.

Working together, the sea lions drive the tuna into an old lava flow...

leading them into a trap.

Now, the sea lions have the edge.

But the scent of blood alerts their rivals.

The bull has his catch, but is surrounded by sharks.

One bite could leave him wounded and unable to support his family.

When it's all over, the bull is unharmed.

But he's lost his prize.

Still, their pup's got to eat.

So Mom isn't giving up.

And the sharks know it.

So, the sea lion's only chance is

to drive the tuna where the sharks can't follow.

Straight out of the ocean.

At last, their young pup has all the food she could want,

thanks to the unique hunting skills of her parents,

seen nowhere else but here...

in the Galápagos.

The global ocean current continues to bring the entire Pacific to life,

taking just four years to cross

the greatest stretch of open ocean on Earth.

Over 12,000 miles wide, the South Pacific.

Where a green sea turtle is hoping to find food.

She's listening out for the sound of distant surf.

Huge swells, driven by winds, break on the shallows,

unleashing some of the most powerful waves in the world.

It's no place for the fainthearted.

Because beneath all these Polynesian waves...

it's gnarly...

as hundreds of tons of seawater can crash down with every barrel.

People have been riding the waves here for centuries...

but the turtle's ancestors have been charging the breaks since long before us.

She knows how to manage herself in the waves.

Unlike some.

Besides, she's not here to surf.

She's here for the turf.

She knows the best algae grows where the coral can't,

in the impact zone, right where the waves break.

And thanks to her skills, she has the best grazing all to herself.

Everyone in the South Pacific has to cope with nature's most powerful forces.

When a volcano exploded in Tonga in 2022...

it released energy equivalent to 1,000 atom bombs...

...sending shock waves around the planet.

But it's in chaos like this that we see the Ring of Fire's most surprising role.

Over millions of years,

eruptions have created a legacy of more than 20,000 paradise islands.

Each one, a stepping stone for life...

helping creatures spread across the vast distance of the South Pacific.

And once in a rare while,

the Ring of Fire combines with the great current

to throw these long-distance travelers an extra lifeline

by carrying rafts of pumice...

which offer safe passage to hitchhikers.

Even as far as Australia's Great Barrier Reef.

And back to where we started our journey, the coral reefs of the West Pacific.

A new home, where the drifters can finally settle.

If they can find a place among the locals.

On our journey around the Pacific Ocean,

the global ocean current has helped transform

the Ring of Fire's destructive nature

into a powerful force for life.

But its epic, one-thousand-year-long voyage...

through all our oceans...

is only just beginning.

Next...

the current flows into the Indian Ocean.

Vibrant...

and spectacular...

but highly competitive.

When faced with the increasing impact of our world,

it's the cleverest...

who will find new ways...

to survive.