Original subtitles

[Alan] Equipment wise, and weather wise,

you psychologically prepare yourself

because with all best intentions

you can plan an expedition for two years,

and you go there and it just goes wrong.

[Victor] Sailors were actually terrified

to come to this area

because it was so dangerous.

And ships did not return.

[Alan] Just watch that arm.

[Kelvin] Up on the towline a little bit!

[bleep] it!

Oh [bleep]

[Patrick] LF.

LF. Comms check. Comms check.

He didn't hear me. He didn't acknowledge.

[dramatic music playing]

[Demetri] Humankind has explored

every continent on Earth.

Climbed its tallest mountains.

And even journeyed into space.

[man] Thank you, Mr. President.

[Demetri] But there's a vast swathe of our own planet

that has remained a mystery.

[dramatic music playing]

[Demetri] The deep ocean.

Stretching down over 35,000 feet into crushing pressures,

it's been near impossible to reach.

Until now.

New engineering breakthroughs

are driving an audacious global mission

to dive to the deepest points of all the five oceans,

for the first time in history.

These pioneers will push technology to the limit...

- What the hell was that? - We have a leaking hatch.

[Demetri] ...to open up this final frontier

as never before.

[Casie] Trying to mentally put yourself at the bottom

is just mind-blowing.

[Demetri] Mapping hidden landscapes,

discovering unknown lifeforms.

[Alan] What on Earth is that?

And unlocking the secrets of how life

in the extreme deep ocean

affects our entire planet.

[dramatic music playing]

[Stuart] Okay, Alan, good to go.

[Alan D] Good to go.

[Demetri] Extreme explorer and ex-naval commander

Victor Vescovo

is putting his life on the line,

as well as 50 million dollars

of his own money to pursue his dream.

Good boy.

What little boy or little girl

doesn't grow up wanting to be an explorer?

And here I am with a wonderful ship, a great crew,

it's now the deepest diving submersible in the world

and I get to play in the ocean with it

and discover things that have never been seen before.

How could you not be absolutely ecstatic?

[Demetri] His mission is to travel to each

of the five oceans, discover their deepest point

and unlock their unexplored secrets.

He has already travelled over five miles down

to the very bottom of the Atlantic Ocean.

[Victor] Oh, my goodness. I can see the bottom.

[Demetri] Now he and his team are heading

for a far tougher challenge.

The Southern Ocean.

It surrounds the frozen continent of Antarctica.

These are the coldest waters on the planet

and some of the roughest seas,

making it perhaps the most dangerous

of all the Earth's oceans.

[Victor] Some of the old-style maps had "here be dragons"

and sailors were actually terrified

to come to this area because it was so dangerous.

And ships did not return.

They would be destroyed.

[suspenseful music playing]

[Demetri] Rising winds are already testing

the crew and equipment.

Getting a little brisk out here, all right.

It's lovely. Might have to take the shorts off.

[laughs] Will have to go to long pants soon.

[man] Boy, it came up [bleep] quick, huh?

[Patrick] Kelvin, you need more straps?

[suspenseful music playing]

[Demetri] Soon, they're experiencing

a full-scale snowstorm.

[Patrick] [bleep] me.

[Stuart] It should be dead ahead somewhere.

I'll just lower the starboard a little bit.

Yeah, I got it.

[Victor] In this life, I'd rather be lucky than good.

And when it comes to weather,

you definitely want to be lucky.

[Demetri] Victor is worried about the effects of the cold

on the expedition's vital navigation equipment.

Batteries look okay.

Modems.

Yeah, these guys did well.

Very strange seeing snow on my landers.

[Demetri] The snowstorm has been an early warning

of the treacherous weather that could lie ahead.

[indistinct radio chatter]

[Demetri] To search for the ocean's deepest point,

Victor and his team are heading for a dramatic

underwater chasm called the South Sandwich Trench.

[Demetri] Over four and a half miles deep,

its waters drop below freezing

and are under huge pressure.

Five times the crushing power of a junkyard car compactor.

[Victor] It's very rarely visited.

And certainly no-one has ever mapped

the South Sandwich Trench.

Certainly not with the kind of tools

we will have available. So in a way,

This is very exciting for the whole crew

because this is true exploration.

[Demetri] To protect Victor from

the deadly pressures at the bottom of the trench,

he has commissioned a remarkable prototype sub

at a cost of 35 million dollars.

Surrounding the cockpit is a sphere

of 3.5-inch thick titanium

punctured by wide-angled view ports made of acrylic.

It's equipped with enough oxygen tanks

to give him air for up to four days.

But in the Southern Ocean, the sub will have to endure

temperatures far colder

than any it's experienced before.

[Patrick] We'll have surface temperatures

that are starting at zero,

or one degree, rather than where we were before

where the surface temperatures

were 25 or 30 degrees Celsius.

At depth, it'll be minus one.

It's enough to affect our cabling,

our connectors, our batteries.

[Demetri] If the dive succeeds,

the expedition scientists

will be able to hunt for unknown creatures

of the deep...

[man] Prepare lights on SCAFF.

[Demetri] ...and try to solve

one of the Southern Ocean's greatest mysteries.

These waters are, in fact,

packed with oxygen and nutrients

vital to life

and are the source of a global ocean current

that feeds the world.

Scientists are desperate to find

where this lifeblood current

exits the Southern Ocean.

The South Sandwich Trench is a prime suspect.

But no-one has been able to dive

deep enough to confirm it.

[Oscar] The Southern Ocean, in my opinion,

is one of the most important locations on the planet.

It's the lungs of Earth.

[Katherine] It's vital to global ocean circulation.

So we need to know more. We want to know more.

[Demetri] To make their bold attempt,

Victor and his team

only have a short window of time.

The brief Antarctic summer,

when the pack ice that locks in

over seven million square miles

of ocean,

melts and retreats.

[ice crashes]

[Oscar] If you look at the Southern Ocean,

every winter we grow

almost the equivalent of the Continental United States.

And in summer, melt that entire continent back.

[Demetri] 100 miles away from the deepest point,

the team sees the chance of a break in the weather

to take the sub on an exploratory dive.

It's an opportunity for Chief Scientist Alan Jamieson

to search for new creatures of the deep

and for Victor to put the sub through its paces

in the Southern Ocean's freezing waters.

In the spotlight is the sub's designer,

John Ramsay.

[John] Mechanically, everything is great

at cold temperatures.

It's the electrical issues

with cold circuit boards and things like that.

Just hoping everything's gonna be fine for the guys.

[Demetri] First, the team needs to launch

their 35-million-dollar sub

off the back of a ship being buffeted by the volatile

Southern Ocean.

[Patrick] The most dangerous part

of any of our operations

will always be launch and recovery.

That's when you're dealing

with forces that are unpredictable,

and managing that is a difficult thing.

[John] Bridge, Bridge SO. We're ready to launch here.

We're roly-poly, but we'll give it a shot.

Okay. Let's do this. Out on the A-frame.

Follow the tagline slowly.

The waves are coming in behind us.

LF, be advised, it's gonna get a little sloppy here

for a minute.

This is where we start to rock 'n' roll.

Here we go, boys.

You're gonna have to go quick. This is the worst part.

[man] Back on the main! Back on the main!

[man] We're out of time.

[man] Up on the towline a little bit!

[bleeping]

[bleep] me.

Just hang on. Hang on, buddy.

Get that out on the tow line! Whoa, whoa, whoa!

[bleeping]

[man] Why are we doing this?

[bleep]

[man] Out on the tow line.

[Patrick] To have that happen right at the moment

you're releasing it.

You know, that's a sickening feeling.

[Victor] Status, please?

[man] Just be advised, uh,

looks like you may have lost your starboard camera.

[Victor] Roger that. Permission to dive.

[man] Negative, negative.

We gotta release the towline still.

- Okay, let's pick up the... - Yep.

[bleep]

[bleep]

[Victor] What happened to the towline?

We broke the towline.

[man] We'll get her, Ricky.

[Demetri] Without its tow line,

the sub is now adrift.

The team must clear the remaining lines

and avoid getting freezing water

inside their protective clothing.

[Glenn] In the cold water of the Southern Ocean,

if you go into the water, you've only got about a minute

before you're in serious trouble.

Let's get ready in case he falls in the water.

What am I supposed to do?

[bleep]

[Demetri] After rough seas

caused the sub to collide

with the back of the ship on launch,

the sub has lost one of its external cameras.

The team can't see any other damage

and decide to press ahead with the dive.

- [man] LF, this is SO. - [Victor] LF, go ahead.

[man] Okay, you're clear to dive.

Clear to dive.

Pumping in. Okay, here we go.

We're descending. We're underwater.

- It's eerily quiet. - Yeah.

[Demetri] The green color of the water here

is evidence of what makes the Southern Ocean

so vital to life around the world.

Plentiful nutrients build up here

during the long, dark winters,

and in the summer feed

explosions of microscopic plants

called phytoplankton.

They bloom in such quantities

that NASA has even been able to track them from space.

[Paula] It was mind-blowing that on that type of scale

in the Southern Ocean, the phytoplankton were

responding to the surface currents

and the winds, and their distribution,

and you could see that from space.

[Demetri] Plants depend on light

and so they live in a narrow band

near the surface,

the Sunlight Zone.

And here, they in turn support an abundance

of microorganisms called krill

which feed a rich food chain, from penguins...

to killer whales.

Passing below 650 feet,

the sub enters the Twilight Zone.

Here, the light dwindles

and the ocean's microscopic plants

can no longer survive.

Yet life does thrive here.

Like this ice fish. Its blood still runs

because it has a natural antifreeze in its veins.

And transparent, jelly-like organisms called salps

that string together in long chains.

[Victor] See, look how dark it is.

[Alan] That's incredible, isn't it?

Surface, this is LF. Present depth, 348 meters.

[Demetri] Victor and Alan have been underwater

for just ten minutes,

but the surface crew have spotted evidence

of a worrying fault with the sub.

[Alan] I think it's best to report, just in case.

- Kelvin, Xeno. - [Kelvin] Go ahead.

[Alan] Yeah, just for you information

Looks like I can see a small oil slick.

[Demetri] It seems that when one of the sub's cameras

was damaged on launch,

it breached the oil-filled pipes

that carry electrical wires around the sub.

It's now only a matter of time

before seawater gets in

and shorts out a vital part of the electrical system.

The sub's power comes from six batteries

packed into detachable pods on either side of the sphere.

They, in turn, link to junction boxes

that supply the sub's components.

To protect the wires and electronics

from the pressures of the deep,

the boxes and pipes are all filled with oil.

Because oil is lighter than water,

it's now escaping from the breach

at the top of the sub,

letting water seep in.

If it reaches the junction box,

it will knock out multiple components,

leaving Victor without full control of the sub

2,000 feet below the surface.

[Patrick] Okay, response. Need you to instruct

the LF to abort the dive.

They're gonna have to abort the dive.

There are times when you have to call it,

and even if it's unpopular, you do it because

you have to do what's safe.

[Response] LF, LF, this is the response.

Please abort the dive.

Abort the dive.

Roger that. Aborting dive.

- Repeat. Aborting dive. - Why?

[Victor] When we lost the camera,

it sheared the cable

- so oil started leaking. - Oh.

[Demetri] Victor must now make a controlled release

of enough diving weights to bring the sub safely

back to the surface.

[Victor] Ejecting weights.

All weights jettisoned. Ascending to surface.

Get ready to brace.

[Patrick] We had to abort you, man.

Cause you would have... you would have lost your...

and you would have lost your modem anyway.

So, at some point, you'd have been coming up

even if you didn't want to.

[Demetri] Repairs to the damaged sub begin.

Try to give it a little bit.

[Demetri] And the team encounter

another deadly hazard

of the Southern Ocean.

Icebergs.

A specialist ice pilot has joined forces

with the captain to navigate

through these unpredictable ship sinkers.

[Berndt] Nine tenths of an iceberg

is underneath the ice.

And I've seen icebergs going against the wind

which is completely not intuitive.

[Demetri] To begin with, the icebergs

are relatively small.

But then comes a monster.

[Stuart] That's the target. It's dead ahead of us now.

[Victor] Is this the biggest you've ever...

I've never seen one this big.

It's extraordinary. It goes off into the horizon.

[Heather] And it disappears off into the fog.

And then disappears off into the fog on the other side.

[Victor] This is massive! How long is it, Stu?

About 18 miles, this one, I think.

It's more than a half marathon long.

You know icebergs actually pose a true danger,

so when I'm coming up from the bottom

I don't want to be going up too fast because I don't know

what's directly on top of me.

[Demetri] Finally, the team arrive

above the South Sandwich Trench,

a vast underwater canyon

that's a staggering 4.5 miles deep.

Their first task is to identify on the floor

of the trench the precise location

of the deepest point in the Southern Ocean.

Using one of the most powerful

sonar scanning systems in the world,

they begin to map, for the very first time in history,

an extraordinary hidden landscape.

[Victor] If this were inverted and was a mountain range,

it would actually be higher

than the entire Andes mountain chain.

It's massive.

[Demetri] The South Sandwich Trench

is a staggering 600 miles long,

stretching from the lower reaches of the Atlantic

down into the Southern Ocean itself.

But up on the bridge,

the team spot a growing threat

to the deep dive.

[Victor] These storms are moving faster than expected.

The two low-pressure systems are causing

all this weather to go in a funnel.

We can't outrun it. We point the ship

into the storm and we ride it out.

[Demetri] In the freezing waters of the Southern Ocean,

an approaching storm is threatening to derail

Victor's attempt to discover and dive its deepest point.

We are in the screaming 60s.

You do not hang out at this latitude

and not have storms come at you.

Even if it's rough weather, we're gonna tough it out,

so we can get the bio samples,

even if we don't dive it.

I would like to deploy the landers.

[Demetri] The landers are underwater scientific probes

packed with sensors, cameras and traps.

They are vital for the team's mission to explore what life

could possibly exist in the icy waters

24,000 feet below.

[Paul] Pretty exciting. I mean, we are

at the limits of this planet.

Basically, ultra-cold and high pressure

is very hard to adapt to.

[Demetri] There are five landers on board,

costing up to $200,000 each.

But with the storm on its way, to launch and retrieve

these near one-ton monsters could put lives on the line.

[Alan] Hope it doesn't storm more. We don't want

ice forming on the deck.

If any one of us fell in the water,

I mean because it's so cold down here,

you get hypothermia pretty fast.

[Heather] Watch out.

[Alan D] Come down the wire.

[Alan J] It's going that way.

Okay, tags off.

[Heather] Lovely job.

[Demetri] Despite the conditions,

two science probes are heading for the seabed.

Eight hours later, and after a remote release,

they are due back on the surface.

But now the weather is taking a dramatic turn

for the worse.

[Alan] The nature of what we do is notoriously dangerous

in terms of equipment-wise and weather-wise.

You psychologically prepare yourself

because with all best intentions

you can plan an expedition for two years

and you go there and it just goes wrong.

[man] Where are they?

[Stuart] I've got it. Okay Xeno,

we have a visual about 800 meters west of us.

[man] Roger that.

[Victor] Oh, man.

[Alan] Just watch that arm, it's just...

if it takes one little roll...

[Victor] It's scary.

[Alan D] Line come down, right.

[man] Going up!

[Alan D] Down, down, down, Down on the wire.

[man yelling]

[Paul] Where is it?

It hasn't worked, no.

[man] We have lost it.

See what happened to the rope?

Looks like something chewed it,

[Demetri] A crucial piece of scientific equipment

and any extreme lifeforms it may have captured

are now plummeting back to the seabed,

never to be seen again.

And now comes more bad news.

The crew have failed to locate the second probe.

[Alan] We should be seeing that strobe

clear as day by now, right?

[Demetri] And because the Antarctic winter

is now fast approaching,

they must abandon the search and move on.

[Paul] Very distressing, yeah we have limited time

and we've got bad weather coming

and we might not get another chance

[Demetri] There is better news for the sonar team

mapping the trench.

Wow. what is that?

[Cassie] This is a sea mound that's 1100 meters

off the sea floor.

[Demetri] The sea mound is an extinct underwater volcano.

Previously unknown, the team get to name it.

It's a stark reminder that we know more

about the surface of the moon

than the seabed of our own planet.

It's just fantastic. I mean, nobody knew

anything about this area.

And look at all the amazing features

that have been imaged by the sonar.

[Demetri] The new data also bolsters the theory

that the South Sandwich Trench is the root

of the mysterious lifeblood current

which feeds the world.

[Oscar] When you carve trenches in the ocean,

you create a funnel where water flows.

Are these trenches reservoirs relatively undisturbed?

Or are they dynamic through-flows of water?

[Demetri] To confirm the theory,

the team need to sample the deep trench itself.

And now, for the first time in history,

they've accurately pinpointed the very deepest site

in the Southern Ocean.

[Cassie] Based on the satellite data,

this one right here has always been the one

that we thought was going to be the deepest,

or this last one.

No one considered a third one.

Now we know the deepest point in the Southern Ocean

is this yellow dot right here.

[Victor] Wow.

[Demetri] A staggering 24,388 feet below the surface.

This is Victor's target for a dive

he's determined to take on alone.

[Victor] Doing things solo,

you're completely responsible for everything that happens.

And you're doing it by yourself

with such intense focus.

It makes it more interesting. I guess for me.

It's more exciting. You're completely on your own.

[Demetri] There are now just days left

before the Antarctic summer ends

and the Southern Ocean becomes too dangerous

to dive.

With rough seas forecast for tomorrow,

it's now or never.

But there are major concerns for Victor's safety.

I don't wanna slam into the bottom of an iceberg.

There are huge bricks of ice out there.

Apartment-sized blocks of ice.

[Demetri] The expedition team are facing a major setback

in their plans to send Victor down

to the deepest point of the Southern Ocean.

Icebergs that could threaten his return to the surface.

Despite the risks, they decide to press ahead.

He's gonna make a very careful and deliberate

return to the surface.

We want to make sure that he verifies himself

with cameras that the surface is clear.

Just in case we have him misplaced on our chart.

Frankly, I'm gonna use light power to slowly go up.

I'm not gonna drop the freeboard to rocket up.

[Demetri] The team prepare to launch Victor

on his historic attempt

into the freezing temperatures

of the deep trench beyond any hope of rescue.

Okay. You're going to have a great dive.

I know. It'll be awesome.

[Glenn] Going to the bottom of the ocean in a submersible

is like going on a space mission

in terms of the isolation.

- [Kelvin] Coming down! - Hatch coming down. Thank you.

Okay, let's do this.

Get him in, boys.

[Glenn] The cold, extreme remoteness

will play on Victor's mind

because if anything goes wrong,

you're right at the end

of the most stretched rubber band in history.

And you're really hoping that we'll pull you back.

[Victor] LF, It's pumping in.

Proceeding to dive.

[indistinct radio chatter]

Roger that, I'll try thrusters down. Thanks.

And down we go!

Looking outside the portal,

looks like a lot of food down here.

Oh, I just saw a jellyfish.

Surface, LF. Present depth.

[man] Present depth, 487.

- Light support good. - Roger that, LF.

We have you loud and clear. Well, that was quick.

Whoo! [laughs]

I mean he is whistling down!

[Demetri] Within just minutes,

Victor reaches the very deepest zones

of the Southern Ocean.

The Midnight Zone.

Where no light at all can penetrate.

And where extraordinary creatures

are still being discovered.

The giant sea spider whose internal organs

are carried inside its legs.

The feather star, which uses the long spines

along its arms to filter out microscopic food

from the water.

And visitors from above. Deep-diving sperm whales

which have the largest brains of any creature

that's ever lived on Earth.

At 13,000 feet,

Victor enters the Abyssal Zone.

Home to sea pigs that inflate up to seven pairs of legs

to walk around the sea floor.

And alarm jellyfish that if attacked

emit bioluminescent flashes

thought to act like a burglar alarm

to attract bigger predators to the scene.

Can already feel the cold coming through the bottom

of the submersible.

[Demetri] The temperature of the saltwater outside

has now dipped below freezing.

I'm checking to see if I hear something unusual.

I don't have any systems on. I'm not using thrusters.

It's almost like a hum.

It does sound like a low hum

coming from outside the sub.

I don't think I've heard that before.

There's so much background noise right now.

Seems to be coming from the submarine,

you can't hear the surface.

Surface, LF.

Present depth, five-zero-three-one.

I cannot read you.

- I cannot read you. - LF,

comms check. Comms check.

He didn't hear me. He didn't acknowledge.

[bleep] what's going on with that thing?

Do you read me? Do you read me at all?

[Kelvin] As a submarine pilot, you don't want to lose

communication with the surface.

That's extremely dangerous. Extremely dangerous.

Status! Status!

What the [bleep] going on where he can't hear us?

[Victor] Surface, surface.

How do you read?

Loud and clear. Loud and clear.

Crystal clear audio. I can hear him.

[Demetri] It's a critical moment in the dive.

Should Victor abandon or continue into the deep?

[sighs] Maybe it's the cold water or something.

3,000 meters from the... from the bottom.

I may just keep going.

I've come all this way.

We're gonna achieve the mission here.

I'm not gonna abort for comms out.

[Demetri] As he descends further into the trench,

it's not just the communications system

under attack from the freezing

Antarctic waters.

The electrical supply to the external cameras

has also cut out.

Well, now I'm really alone.

I don't have comms to the surface,

I'm in a submersible by myself,

going down to the bottom of the Southern Ocean.

[rapid beeping]

[Demetri] In Mission Control, it's been two hours

since they last made contact with the sub.

Attention all stations.

Be advised that we can hear Victor

but we cannot communicate with him.

He cannot hear us.

He's very close to the lander.

[man] I'd say within a couple of hundred meters,

so he must be near the bottom.

Insulation fault. That's probably

just some water residue in there.

Everything's looking good.

I should be getting really close now.

Oh, my.

I can see something on the bottom.

I'm seeing the bottom much more clearly.

I've just reached the bottom of the Southern Ocean.

Looks like a moonscape out of one of my portholes.

Surface, LF. At bottom. Repeat. At bottom.

- On the bottom. - [cheering]

[clapping]

I am at bottom.

I'm at the bottom of the Southern Ocean.

[Demetri] Victor is an amazing 24,388 feet

below the surface.

Where no human has ever been before.

The team have also deployed here

their three remaining science probes,

or landers, baited with tempting fish carcasses.

And although Victor's external sub cameras

may have cut out,

amazingly, the cameras

on the landers are still working.

They now capture Victor's arrival at the bottom.

His lights just visible across the sea floor.

These are the first ever images captured

at the bottom of the South Sandwich Trench.

And attracted by the lander's bait,

there's already a crowd of super-strange specialists

able to endure intense cold and enormous pressure.

[Victor] See tiny white... they're like perfectly white.

They look like tadpoles.

What's that over there? A larger creature.

A little pink on the... on the top.

It has a little pink head. Two big eyes.

Oh, he's definitely swimming.

He's swimming away from my blast.

[Demetri] It seems that Victor has identified a mysid,

a type of crustacean whose bright red color

in fact makes it even more invisible

in the pitch dark of the deep ocean.

1500 feet further up the trench slope,

a second lander is capturing remarkable images

of the range of life that thrives here.

Sea lilies, and tall, tubular glass sponges.

Both snag passing microorganisms

drifting past in the current.

And higher up the slope still,

a third lander is capturing the first ever footage

in this trench of a truly remarkable creature.

Known as a snail fish,

this is the deepest-living kind of fish yet discovered.

And here are two new species

filmed for the very first time.

The snail fish are not here for the bait itself,

but to pick off any scavengers

the bait attracts.

Finally, the landers'

auto-release mechanisms activate,

and they head back to the surface.

But now comes the massive challenge

of safely retrieving

these 200,000-dollar pieces of equipment

in heavy seas.

- What do we got? - [woman] I think I'll just

be happy if it lands on deck.

Oh, [bleep].

The most difficult side to catch it on,

because of the arm.

[Demetri] Having lost two landers already,

the pressure is on.

[man] Charlie, we're gonna have to cross the tag lines.

[woman] Yeah.

Oh. Don't lose your balance.

[man] Oh, this thing is a nightmare.

Whoa. Got it. Got it. Wait, wait, wait.

- [man] All right, got it. - [woman] Good.

Right, what does the bait look like?

Oh, here we go.

[Alan] It's absolutely freezing.

[Demetri] The team have a vital hoard of specimens

from 24,000 feet down

whose chemical secrets could set the stage

for scientific breakthroughs in the future.

[Paul] Hopefully, we'll discover new molecules

that have to do with combination of pressure

and ultra-cold temperatures.

Those may have all kinds of applications.

In China, they've been able to use the osmolyte

that we discovered in deep-sea animals

to actually cure glaucoma,

which is a high-pressure disease of the human eye.

[Demetri] Sensors on the landers

have also brought back vital information

that could confirm the root of the lifeblood current

carrying nutrients from the Southern Ocean

to the rest of the world.

The data is dispatched to the British Antarctic Survey

in the UK, where a team have been tracking

the current at shallower depths.

[Hugh] The data we were very kindly given

confirm that this is Antarctic bottom water

and that it is going through this trench.

The actual flow through it is tens of times the flow

of the Amazon. Millions of tons a second.

[Demetri] It's a breakthrough that will be vital

for future scientific work.

[Hugh] We can measure the waters flowing through

to see any change, see any signals

that are happening before it spreads out

across the whole of the world's ocean floor.

These very deep data

are gonna be very valuable for a long time.

Okay. I think that's a wrap.

Surfacing light release.

And we're heading up.

[Demetri] Two and a half hours after leaving the bottom,

Victor is now approaching the surface.

But after his radio and cameras

cut out in the cold,

he has no way of knowing

if there's an iceberg in his path.

If there is, the sub could be pinned

beneath the ice with no way out.

I'm just gonna come up slow.

Hope I don't hit an iceberg.

If I hear a thump, I'm stopping quick.

Going up. Just be patient, Victor.

100 meters to go.

[man] LF, comms check. How do you read?

[man] Yeah. Do you have visual?

Hang on.

[Victor] On surface. Repeat. On surface.

- [man] Yeah, we can see you. - I see him now, I see a light.

[man] Welcome back, Victor.

Thank you, gentlemen. It's good to be back.

[man] Xeno is inbound,

should be there in any minute.

[Victor] Roger that. Xeno inbound.

[man] We had some comm issues,

but we're gonna talk about that after.

Just glad to have you back on the surface

and just rigging for recovery.

Roger that. Comms were a problem,

but the mission was a success.

[man] Indeed it was. Indeed it was, sir.

- Great job. - [Victor] Thank you, sir.

[man] Just Nice and slow. Nice and slow.

[Demetri] The sub may be safely back on the surface,

but there's a final challenge to overcome

in the volatile waters of the Southern Ocean.

- [man] Ride that thing, Steve. - [Steve] Okay.

Oh, that was a big wave, guys.

[Steve] The LF does not like being on the surface.

It's designed to just dive.

Get to the bottom, get there quickly.

And she's like a wild horse,

like you can try to put a rope on it

and it just fights you, right?

Up on the main.

- Get it, Steve. - [man] Get down on the main.

Come on, Steve. Get... Go, go, go.

- Go! - Come one, Steve.

[man] Two hands, man.

Up on the main. Up on the main.

That's good. That's good, Patrick.

Good job, buddy.

Okay.

How you doing, Steve? You wanna get off there?

I can jump in there and do this.

Steve, let's get you off. No, he's too cold.

Hang in there, buddy.

Steve, let's get you off.

[Demetri] To prevent the onset of hypothermia,

the expedition doctor must bring

Steve's body temperature back up.

He's sat him down next to the heating duct

in the sub's hangar.

Finally, Steve's warm enough to be moved inside.

[indistinct chatter]

Yeah, they're the right color.

Keep using your hands. Good work, man.

- Thank you. - Good work.

[Steve] I've lived on the Tropic of Capricorn

my whole life,

that's close to the Equator,

I don't do cold water. [chuckles]

- [man speaks indistinctly] - [man] Welcome back, Victor.

[Victor] Thank you. Good to be back.

[cheering and whistling]

Good job, team!

[Demetri] At last, Victor is safely back on board.

He's now the only person to have reached

the deepest point of the Southern Ocean.

The second of his five deeps.

- Good to be back. - It's good to have you back.

[Victor] Some interesting moments,

feeling quite alone

in the middle of the Southern Ocean,

but we got it done, it's good to be back.

All right. It's kinda cold.

[laughs]

Ha-ha! Thanks for getting me back.

It's a very high-tech machine that we took

to a very inhospitable place.

And it was extraordinary.

We're doing it because we're explorers.

Because we want to see.

We want to push the boundaries.

We want to learn things

that haven't been learned before.

And we want to do it together and bring it back

and share it with other people.

[mellow music playing]