Original subtitles

NARRATOR: A lost relic from one of history's darkest periods.

- What have they found hidden under 61 metres of water?

NARRATOR: Cryptic ocean patterns reveal a hidden talent.

- It's like a giant question mark, begging you to answer its riddle.

NARRATOR: A post-apocalyptic landscape lost at sea.

- It looks like it was hit by a bomb.

NARRATOR: Mysterious markings dot the deep abyss.

- The bottom of the ocean is the last frontier. What dwells there?

We still don't know.

NARRATOR: Everywhere we look on our planet,

there's evidence of the past. In nature, in buildings, in relics.

Each holds a mystery that technology now allows us to see from above.

What new secrets are revealed?

We know more about the topography of Mars than we do about what

lies beneath our oceans and seas.

To decipher some of these hidden mysteries we often need

a view from above.

The small island nation of Malta lies in the central

Mediterranean sea.

In its capital city of Valletta, a team of marine archaeologists

prepare for a mission.

Dr Timmy Gambin from the university of Malta has spent a lifetime

searching for submerged secrets.

- When I hear the words Mediterranean Sea,

I think immediately of the great ancient empires that thrived

around it: the Egyptians, the Greeks, the Romans.

The whole area is a treasure ground for historians.

- 71% of the Earth's surface is covered by water.

And, much of it, like the Mediterranean Sea, has never

been fully explored.

- You've gotta ask what else is hiding down in those murky depths?

There could be ancient treasure. There could be buried cities.

NARRATOR: On this day, Dr Timmy Gambin and his team

have only one mystery on their mind.

A strange shape discovered from above during a routine sonar

survey of the sea floor a year earlier.

- The discovery was made possible by a technology called side-scan

sonar that produces an accurate record of the ocean floor.

- There's clearly something there, but you gotta ask, what is it?

NARRATOR: The shape appears to be roughly 8 metres in length.

- This thing, whatever it is, is really pretty large.

I mean, it's about as big as a London double-decker bus.

NARRATOR: Dr Gambin is no stranger to finding fascinating things

around his home island.

- Marine archaeology is truly unpredictable.

You never know what you're going to find.

The sea is just full of secrets.

NARRATOR: In 2007, the Mediterranean yielded one its greatest treasures.

Spotted during another offshore survey, this anomaly turned

out to be a Phoenician cargo vessel dating back to the 7th century BC.

- That Phoenician trade ship is considered to be the oldest

shipwrecks uncovered in the central Mediterranean.

- Could this be another vessel?

NARRATOR: That ship measured 12 metres in length.

This object is slightly shorter.

- So based on the measurements, it's very possible that this, too,

is a ship.

NARRATOR: On the other hand, it could be nothing.

- Not everything here is of historic value.

Sadly, some of these waters are absolutely choked with

debris, ranging from plastic bottles to entire refrigerators, even

shipping containers.

NARRATOR: Luckily, the strange object doesn't appear to be just

rusted out sea junk.

But what's more telling is it's distinct shape.

- A closer look clearly shows the unmistakable outline of an airplane.

- But what kind of plane? And how long has it been there?

- Certainly this part of the Mediterranean is under a very

busy flight path for countless commercial and private planes.

And no doubt more than a few have sadly crashed over the decades.

NARRATOR: But none of the recorded crash sites are anywhere near

Dr Gambin's target.

- It's so frustrating to know that something is down there but

you can't tell what it is.

And there's only really one way to find out and that's to get a

view from above below.

- Okay, let's get into the water and see what the site has to

offer, okay?

Let's remember we need to try and see if we can identify what

type of plane it is.

NARRATOR: Their goal is to capture enough images to produce a 3D

model of the plane so the team can unlock the mystery of what it

is and how it ended up 61 metres underwater.

- Imagine the height of the Leaning Tower of Pisa, that's how

deep down they have to swim.

NARRATOR: To accommodate for decompression, the team will have

a short window to investigate and film the wreck.

- As I'm approaching the wreck, there's a massive sense of

curiosity.

I have a number of ideas of what the aircraft could be.

However, there is nothing certain until one sets one's eyes on

the wreck itself.

NARRATOR: As the divers descend deeper,

the mysterious shape finally reveals itself.

- The first thing that strikes you is that it's sitting perfectly

upright on the seabed.

- It's as though its still taxi-ing on the runway.

This means that the pilot did a great job at ditching the air craft,

because there isn't a lot of damage.

I'm swimming around the wreck looking for telltale signs.

We're looking for small hatches that are distinctive to a particular

aircraft. One has to retain a bit of composure because I'm excited.

I'm seeing the tail of a plane covered in marine growth,

sponges, some other barnacles.

- Now this suggests this plane has been here a very long time.

NARRATOR: Up close, it's clear this is not a modern plane.

Perhaps it's connected to Malta's not-so distant past.

At the height of WWII, the entire region was a deadly

battleground for control of the Mediterranean.

- By July 1942, Hitler controls most of Europe and he's gaining

ground in North Africa.

He needs to control the waterway that links them, the

Mediterranean Sea.

- The only defence against Hitler right there is this handful,

a mere handful, of RAF pilots stationed in Malta.

And the Nazis are trying to make sure they don't get in their

way by trying to bomb this small island nation into submission.

- In summer of 1942, this makes Malta the most bombed place

on the planet.

- So is this plane on the seafloor a Nazi plane?

Or is it a British aircraft, whose job was to defend against

Hitler's forces?

NARRATOR: The heavy marine growth is obscuring any identifiable marks

on the plane.

The team has successfully taken 1000's of photos to build a

3D model of the wreck for further analysis.

- Did you get footage?

- Good footage

- Very much a single seat aircraft. It's absolutely beautiful condition.

Wow, wow, wow. "Bravo".

NARRATOR: The team has discovered a WWII fighter plane.

Could their footage unlock the secret of what kind

of plane it is, and will it reveal how it ended up lost

for almost 80 years beneath the ocean waves?

Back in Valletta, Timmy and his underwater cameraman

search for answers using a 3D model built from footage taken during

their dive of the wreck.

- Oh wow. Yes. There, there, there it is.

- Not bad, eh? - Not bad at all. Wow.

To me, it looks Italian.

It looks like a Macchi 202, but it's slightly squatter.

You know what, John?

It could actually be... Let me look up on my database.

It's still an Italian plane, but I think we may have a

Reggiane Re.2001.

Can you zoom in? Oh wow, so yeah that's it.

This is an astonishing find.

- The Reggiane 2001 was a really quite an advanced piece

of WWII machinery.

Actually, it was a formidable fighter plane.

- Only about 250 were ever produced, making it one of the rarest

planes on Earth.

- Because of its manoeuvrability and speed, it was the pride of

the Regia Aeronautica — the Italian Air Force.

- Since Italy was one of Hitler's allies in WWII, it means that

this wreck they found is a long-lost enemy plane.

- So the question remains, how did it get here?

- For a fighter plane to go down during the Battle of Malta,

only two real possibilities exist.

Either it was shot down during a dog fight or it was blasted out

of the sky by anti-aircraft fire.

NARRATOR: During the battle of Malta, the island's defenders

were armed with powerful anti-aircraft weapons

called flak guns.

Flak guns worked in concert with other batteries unleashing

sustained barrages at predetermined angles and heights —

covering their own 'box' of the sky with withering fire.

- It has a projectile that explodes at high altitude and this sends

out these jagged metal fragments that tear aircraft apart.

- It is not easy to distinguish damage from anti-aircraft guns from

damage caused by other aircraft.

However, there are some telltale signs.

I can see some damage.

NARRATOR: A closer inspection of the wreck's 3D model

uncovers a vital clue.

- I'm noticing damage on the starboard wing, which seems to be

coming from shots fired from another aircraft that is actually

flying at the same level.

If I had to give a verdict, I'm saying that the plane was

shot down by another plane approaching head-on.

- Now the mystery becomes who shot this plane down, and why?

- As a formidable fighter plane, the Reggiane 2001 could dogfight

with the best of Allied planes.

As such, they had the respect of RAF pilots.

NARRATOR: Except for maybe one:

George "Buzz" Beurling.

- As one of Canada's greatest ace fighter pilots, Buzz Beurling

was so skilled at aerial dogfights over the Mediterranean that

he was known as The Falcon of Malta.

NARRATOR: Buerling is credited with shooting down 27

enemy aircraft over Malta in just 14 days, at least two of which

are recorded to be the ultra-rare Reggiane RE.2001s.

- It's amazing to think this particular aircraft is such a

rare specimen and possibly a tangible relic of the

astonishing kill record of flying Ace George Buzz Burling.

- This is a great example of the mysteries that lie buried

under the world's deepest waters and could only be uncovered with

technologies that peer down from above.

- Any historical memory contributes to ensure that the suffering

endured by our Maltese ancestors is not forgotten.

Any artifact that can be connected with this epic battle for

Malta is an object to be cherished.

NARRATOR: From a strange shape uncovered deep below the waterline

to those spotted at the very surface, a view from above tackles

yet another ocean mystery.

Over 16,000 km away, the coast of Australia's New South Wales

boasts some of the world's most famous beaches.

- Visitors from all over the world come here to soak-up the sun,

surf and sand and bask in its natural beauty.

NARRATOR: Just off these golden shores, something else beautiful yet

bizarre can be seen from above, rising from the deep blue

waters of the Tasman Sea.

- In the distance there appears to be something rising up out of

the water.

It looks like bubbles.

They're forming these beautiful and brilliantly intricate patterns.

- This S-shape pattern looks like a giant sea snake, like

something prehistoric.

- It's like a giant question mark, begging you to answer its riddle.

- So what are these strange patterns in the ocean?

NARRATOR: And who or what could be causing them?

- When I see all these bubbles coming up in such an orderly

fashion, I think of something man-made like a machine.

- Ocean researchers are using this new class of remotely-operated

underwater vehicles like AUVs and ROVs that are known to cause

splashing when they come up to the surface.

- So these small robots are being used to collect data on

everything, including hunting for new species that might exist.

- So could these small submersibles be creating these weird circles

and spirals?

- When you look at how things are being used by researchers,

it's actually an elaborate process.

You need a large boat and a crew to run them.

But here, there's none of that.

- There's no sign of human activity anywhere. So what's causing this?

Could a military submarine be creating these designs when

they go underwater or come back up to the surface?

- Are we seeing some kind of Australian Navy exercise?

- But when submarines dive and resurface, they do it in a

straight line, not in a circle or a spiral like what we're seeing

here from above.

- What is going on underwater to make this happen?

NARRATOR: Perhaps a clue could be found some 8,000 kilometres away

in Japan's Naruto strait, where a view from the air reveals

an extraordinary sight.

- This is an incredible and powerful display of the forces of nature.

This is the Naruto Whirlpools.

NARRATOR: A mighty clash of fast and slow flowing tides, producing one

the world's greatest tidal currents.

- These monster tides create whirlpools that spin at

speeds of up to 20 km/h!

- You've got all this violent water action creating these really

interesting spiral patterns.

Is that what's happening back in Australia?

Are those designs the result of natural whirlpools?

- The powerful tides of the Naruto Strait do create interesting

patterns on the water, but they're not quite like what we see

here from above off the coast of New South Wales.

- The speed and shape of these spiralling patterns is different.

It's considerably slower and the circles and spirals aren't

whirling at all.

NARRATOR: So if it's not whirlpools, could these patterns be made by

something else from the natural world?

Below the water, a clue.

- When you drop down from the air and go underwater, you can see

that these patterns are made up of millions of foamy bubbles.

- The question is who or what is creating these bubbles?

NARRATOR: Perhaps the answer lies roughly a 600 metres off the coast

of New South Wales, with a view from above of nearby Cook Island.

- This island is covered by what looks like layers of lava.

- Clearly there's evidence of previous volcanic activity here, and

it reminds us that to the east of New South Wales lies the edge

of one of the most intense volcanic regions on Earth.

- Is this strange pattern caused by an underwater volcano releasing

vapours and gas through vents in the sea floor?

NARRATOR: This region is outside the most southern section

of the Ring of Fire.

A rim of seismic activity that surrounds the pacific ocean.

Nearly 75% of all volcanoes occur along this ring,

most erupting underwater.

Cracks in the seabed, known as fissures, exposes molten

magma to the much cooler water.

Could these bubbles be the result of this instantaneous blast of

steam and gas?

- But then why would they form circular and spiral patterns?

I mean, this doesn't seem to add up.

NARRATOR: Perhaps a closer view from above can reveal the mystery.

- There's something alive down there. What is it?

And what the hell is it doing?!

- Whatever it is, there's definitely more than one. Are these dolphins?

- So it certainly could be.

I mean, some scientists have observed that when dolphins

mate, they do create these circular patterns in the water's surface.

NARRATOR: But even from high up, it's clear that whatever is stirring

in these strange patterns is larger than dolphins.

So what kind of creature could this be?

- The coast of New South Wales is home to very large sharks, like

the great white.

- And sharks are certainly known to move in circular patterns

when they're feeding in large groups.

- Oh my God, are we looking at a massive feeding frenzy?

- Is that what's causing this bizarre pattern?

A bloodbath below the surface?

- But when you look at sharks underwater, circling their

prey, they don't create any patterns per se, just a lot of splashing.

- And that's because they feed from below, right.

If these patterns are being caused by a marine creature feeding,

then they're actually feeding close to the surface.

NARRATOR: A closer look reveals that these are much, much bigger than

even the biggest of great white sharks.

- So we can tell by the distinctive shape of their back when they

dive and these very long pectoral fins that they are actually

humpback whales.

- Their long, white, flippers are also a dead giveaway.

They're nearly one-third of their body length.

- Which is saying a lot since they can reach a length of more than

18 metres.

NARRATOR: So what we're seeing from above is a rare super group

of humpback whales, animals that typically travel in small groups

of two to a dozen.

- But why are they here?

And how or why are all these humpback whales creating

millions of bubbles to make up these strange patterns?

- I mean, these creatures are super smart, but they wouldn't be

making these just to amaze us with their beauty.

- So, what's its purpose? There has to be a more practical reason.

What is it?

- Humpbacks, like other mammals, breathe air, and so unlike

fish, they can't breathe underwater because they don't have gills.

So what they'll do is they'll come up to the surface of the

water, they'll inhale air through their blow hole and then

they'll begin their dive.

NARRATOR: Underwater, the whales can use that same blow hole to exhale

and blow bubbles.

- But why go through all that trouble?

Why blow these bubbles that form these intricate patterns?

NARRATOR: Perhaps a view from above from over 15,000 kilometres away in

Canada's far north can shed a light on the mystery.

- This looks a lot like what we're seeing back in Australia.

- Except these aren't humpbacks.

These are narwhals, beluga-sized whales that live in the North

and that are equipped with these long and unicorn-like tusks.

NARRATOR: These narwhals are actually hunting together

as a group, using their tusks as a tool.

- Narwhals have learned to smack their tusks on the water to stun

fish making it much easier to eat them.

- Is that what the humpbacks are doing in Australia?

Instead of using tusks, which they obviously don't have, could

the whales be using bubbles to make it easier to feed?

NARRATOR: This kind of behaviour among marine animals

has been observed before.

It's a phenomena scientists call bubble-net feeding.

- In bubble-net feeding, whales will work together by blowing bubbles

that draw the fish or krill in an increasingly tight circle or net.

So once their prey is nicely bundled, the whales can come

up from underneath and gobble them up.

- That's absolutely amazing.

So that's why you see this nautilus shape from the sky.

- Think about how much coordination and lung capacity is needed

to blow the bubbles in this incredible pattern.

NARRATOR: But something about this view from above isn't quite right.

- So humpback whales aren't known to feed in this region which is

why when I see this bubble-net feeding, I'm pretty surprised.

NARRATOR: Humpbacks typically feed thousands of kilometres away, in the

colder waters of the south pole.

- In Antarctica, pods of humpback whales will regularly

bubble-net feed and make these same spectacular designs in the ocean.

- But Antarctica is several thousand kilometres away from Australia.

- So humpbacks don't usually feed here.

They normally use these waters to migrate back and forth.

And during that migration, they fast,

for weeks and sometimes months.

- So why are they suddenly bubble-net feeding here?

NARRATOR: The answer might lie in the water itself.

- So in our oceans, we're seeing changes to currents, changes

to sea temperature, and these changes are likely to impact

where and when certain species feed and also what feeds on them.

- What this view from above shows us is how nature in response to

climate challenges is learning how to survive in a changing world.

- This behaviour is not instinctual, it's learned.

So some populations of humpback whales don't do this because

they've never been taught.

So we're not just seeing feeding, we're seeing learning.

We're seeing a cultural event.

- And that's mind-blowing to see it with your own eyes.

Whales are absolutely magnificent creatures.

NARRATOR: But, at the same time, this rare view from above is also a

stark warning.

- The emergence of these new feeding patterns could significantly

impact other microorganisms like plankton which feed off the

waste that whales produce.

- The use of drones has definitely revolutionized the way in

which we learn about species, like humpback whales.

- Seeing nature like this from above is definitely a game changer.

It allows scientists to document behaviours not necessarily

seen before.

- And in the process give us insight into the future of marine

ecosystems.

NARRATOR: The danger with scanning the world's ocean from above is that

sometimes you come face to face with a ghost.

Just off the southern coast of Japan, an ominous form rises

from the waves.

- What you've got here is this massive, grey structure and

its standing all by itself in the waters.

- From the air, with its elongated shape, it looks like a battleship.

NARRATOR: Clocking in at 480 metres in length and 150 metres in width,

this maritime monolith towers over the surrounding sea.

- It appears to be some kind of enormous, floating city of

concrete, but where are all the people?

- It has this really eerie atmosphere of abandonment.

I mean, I've never seen anything quite like it.

- What is this place?

NARRATOR: A seemingly lonely concrete bastion in a vast ocean.

A view from higher up reveals a clue.

- When you take a step back, the first thing you notice is how close

this place is to the Japanese port city of Nagasaki.

- Nagasaki has been a major manufacturing centre and ship

building hub for centuries.

And at no more critical time than during the Second World War.

- Nagasaki was vital to the Japanese war effort.

It's where their heaviest and most powerful warships were made,

including the pride of the imperial fleet — the Yamato class Battleship.

- For control of the South Pacific, it was all about sea power.

- So it stands to reason that the Japanese would go to great

lengths to defend this key port city.

- Is that what we're looking at here?

Could this be a remnant of some sort of WWII-era maritime fortress?

- When you take a closer look, you can see this place is entirely

made of concrete.

And when I see this much concrete, I think fortifications.

- Concrete was crucial for the construction of bases,

defensive lines, bunkers and gun emplacements.

- During the war, the world went concrete crazy, and its

construction applications reached a whole new level.

NARRATOR: Examples of these wartime innovations lie a world away

in America, at the unique ship graveyard in

Kiptopeke State Park, Virginia.

- This is so bizarre, so creepy. What are these?

- By 1942, there was a global shortage of steel

to produce warships, but there was plenty of sand, gravel, water,

and crushed stone.

- Which are the perfect ingredients to make concrete, and so that's

what the military started using to build its ships.

- When we say concrete, we mean ferrocement, which is

essentially reinforced mortar or plaster.

And that is applied over metal frames to make a ship's hull.

- The Concrete Fleet, here in Virginia, has 9 of the

original 24 concrete ships that the US Navy built for WWII.

They were permanently anchored here in 1948 to protect the nearby

shoreline from severe weather.

NARRATOR: But this ghostly form in the East China Sea

is very different.

- This is no mortar or plaster construction.

This whole thing is made of solid concrete. This could never float.

- This place is clearly not a ship.

It could be some kind of coastal defence, but then why is it

out here in the middle of the water?

- As the name implies, coastal fortifications are, well, on

the coast. Sea forts, however, are not.

Instead, they are structures usually built on artificial islands

away from the mainland.

- Sea Forts have existed in one shape or another for centuries and

this really reminds me of the Bull Sand Fort

off the east coast of England.

NARRATOR: Built for the first world war, but only used in the second,

this stand-alone fortress resembles what we see here in Japan but is

much smaller and compact.

- The Japanese are renowned for taking good ideas and making them

bigger and better.

- And despite being shaped like a gigantic battleship, we don't

see any evidence of gun emplacements or battlements.

Instead, we see signs of a long-lost community.

- So if this place isn't a fort, what is it?

NARRATOR: A closer look from above reveals another important clue.

- You can see buildings and other clear signs that people lived here.

- Was this some kind of island settlement?

But if so there's nothing around?

I mean, why would anyone want to live out here?

NARRATOR: This is Japan's mysterious Hashima Island.

Because of its unusual shape, its nickname is Gunkanjima,

meaning battleship island.

- You've got what look like apartment buildings.

Clearly, this used to be home to someone.

Is there anyone still living there?

- Whatever this used to be, it's now a mere shadow of its former self.

But why are there no signs of life?

- It looks like it was hit by a bomb or something equally devastating.

What was it?

- There's some pretty big questions here.

I mean, how and why did this island become a ghost town?

I mean, what happened here on Hashima Island?

NARRATOR: From above, various clues litter the island.

Objects that don't belong in most residential settlements.

- What you can see all this really heavy-duty industrial

equipment and it's just rusting away.

- Some of it looks like it dates back as far as the early 1900s.

What was it used for?

- If this island had an industrial purpose, what was it?

What were they making here?

- Why would you build a factory in a place that's so difficult to get to?

NARRATOR: The answer might be found nearly a kilometre below the sea,

where, in 1810, an extremely valuable discovery was made.

- If you know what you're looking for, the ocean floor is a vast

treasure trove.

There are all kinds of valuable minerals and precious metals

down there, like silver and gold.

- It's estimated that there could be as much as $700 trillion

worth of gold under our oceans.

NARRATOR: So was Hashima Island once a booming gold town that went bust?

- That certainly would explain why it was abandoned.

The gold mining could simply have just dried out.

- There are certainly many examples of this type of abandoned

settlement around the world.

For example, Ruby, Arizona, a gold town founded in the late

1800s, shut down in 1940.

- For 70 years, Ruby produced not only gold but silver, lead, zinc,

and copper.

- Is that the mystery behind this island?

Is Hashima a gold town that's now become a well-preserved ghost town?

NARRATOR: The answer lies in not what is above the island

but what is below...

And that's coal.

- That discovery would have been huge news for Japan, because in

the Second World War, Japan was desperately looking for ways to

fuel their ships and coal would have been almost as valuable as gold.

NARRATOR: To extract the coal, engineers created

vertical mine shafts below the island, leading to kilometres

of underwater tunnels that increased coal production.

- By 1950, the coal mine was extremely productive, yielding a

monthly average of 14,000 tonnes of coal.

- This island is six hectares in size, roughly two-thirds as big as

Alcatraz Island.

So this coal mine operation was massive.

NARRATOR: Because of its isolated location, the mine was designed and

built with a permanent home for its workers and their families.

- They used all this concrete and steel to build apartment buildings,

a rooftop garden, a religious shrine, even a public bathhouse.

NARRATOR: By 1959, with over 5,000 inhabitants on just six hectares

of land, Hashima Island becomes the most densely populated

area on earth.

- That is simply incredible.

Because of a rock they find at the bottom of the sea, this

island is transformed into a densely populated concrete city with

residential buildings and amenities.

- But all that's left now are these crumbling, ghostly buildings

and ruins.

- This was such a vital community, but where did everybody go?

- Something made these people leave and never come back. What was it?

- What happened here on Hashima Island?

- According to official records, the working conditions for the

miners were brutal, often reaching temperatures as high as

38-degress Celsius.

Miners collapsed on a daily basis.

NARRATOR: As many as five workers died every month,

victims of industrial accidents.

- Back then, modern concepts of safety were non-existent.

The corpses were cremated on a nearby island.

- Is that what turned Hashima into a ghost town?

Did the labour force just quit and leave?

NARRATOR: The island's decline was not caused by a dwindling workforce

but instead by the cheaper abundance of oil and gas and the meteoric

rise of the automobile.

- With the worldwide popularity of cars, petroleum was gaining

popularity in Japan as an alternate source for coal.

So, by the 1960s, you started to see coal mines shutting down

pretty much across the country.

NARRATOR: By January 1974, Hashima's coal mine was formerly closed.

Three months later, everyone now out of work, island residents

were forced to leave their beloved homes behind...

forever.

- But with living space at a premium in Japan, why hasn't anyone

returned or developed the island for residential use?

- From above, you can see how the ongoing action of the waves

and the weather have reduced the concrete to rubble and

corroded the steel structures.

So that would pose a threat to anyone that would try to live here.

- Every year, more and more of the island's crumbled concrete

gets taken into the East China Sea.

NARRATOR: At its current rate of decay, Hashima Island, and its

unique place in history, is destined to be swallowed beneath the waves.

- It's incredible to me that in the middle of all this water you

come across what was once the most densely populated area on Earth.

- All this history captured on this one little island.

- This is a story that can only be fully appreciated and

actually discovered from the air.

NARRATOR: From a mystery discovered on the surface of a sea to one

hiding in the ocean's depths, a view from above uncovers a secret

never before seen by human eyes.

In the Mid-Atlantic ocean, 480 kilometres east of Portugal's Azores

islands, marine researchers

for NOAA, the National Oceanic and Atmospheric Administration,

deploy their research vessel to get a unique view from above,

below the ocean's surface.

- As this camera's moving farther down, it's getting closer to

the centre of the Earth. It's got more and more water on top of it.

You can just feel the pressure getting more and more intense.

- Because of the pressure, no human can dive this deep.

- That's why they're using these remotely operated vehicles or ROVs.

- This view from above is really the only way to get a glimpse at

this dark abyss.

- Roughly 75% of the ocean's floor is unmapped, so you're never sure

what species you're going to come face to face with.

NARRATOR: This strange, dark world is home to an untold number

of unique organisms, many of whom remain unknown.

With little oxygen, no light, frigid temperatures, and extreme

pressure, it's a wonder there's life in this part of the world.

- This is very freaky stuff.

NARRATOR: Remarkably, of all the wondrous things the team from NOAA

have seen here in the deep ocean, nothing is more inexplicable

and mysterious as what they see next.

- There we go. They're elongated holes.

It is peculiar to have the holes in such a straight line.

- And the regularity of the spacing.

- And a whole chain of them.

NARRATOR: What can this series of seemingly random trails of evenly

spaced holes on the ocean floor tell researchers?

- It's a little bit eerie.

There's nothing else around them, just these little tracks in

the sand.

- They're so perfectly spaced.

I mean, why would it always be that spacing?

- No, that's really, that's really odd.

- It seems really symmetrical.

As if Poseidon had come along and started jabbing his trident

into the bottom of the sea.

- What are these mysterious holes? Where did they come from?

- And who or what created them?

NARRATOR: Maybe the view from above can reveal a possible clue?

This is the Mid-Atlantic Ridge, a mountain range that runs for over

16,000 kilometres along the length of the ocean floor.

- It's part of the longest mountain range in the world.

- In terms of geology, that ridge is hugely significant.

In the North Atlantic, it separates the North American, Eurasian,

and African Tectonic Plates.

And in the South Atlantic, it separates the South American

and African Plates.

- And where there's the meeting of tectonic plates, there's volcanoes.

- The Mid-Atlantic Ridge system is actually a continuous range

of underwater volcanoes, wrapped around the globe.

- Is that what's causing these holes?

It's the beginning of an underwater eruption?

Is the whole sea floor about to blow wide open?

- But when an underwater volcano is active, there's also a

significant number of bubbles because it's seeping gas.

I don't see any of that here.

- Ongoing volcanic activity also tends to leave behind these yellow

sulphur deposits.

You don't see any of that yellow stuff here.

- So how were these holes created?

- I mean, it looks like it must have been a machine.

- I mean, that, that's... - It does look like sprockets.

- Yeah, that looks rectangular to me.

NARRATOR: Even the experts marvel at the uniformity of these strange

deep water cavities.

- They're almost, um, blade-like.

- I mean, it looks like somebody had a bicycle with spiky wheels and

they rode it along the bottom of the ocean.

NARRATOR: The pattern is similar to farming techniques used on land to

produce evenly spaced out holes for seedlings.

- Who could possibly be toiling away here three kilometres down in

the darkest, deepest corners of the Earth?

- As far we know, this is the first time humans have ever laid

eyes on this part of the ocean, so it seems highly unlikely any machine

has ever reached this part of our planet, never mind worked its soil.

So what could it be?

- Is there something underneath?

Are these holes just a little window into something even more

mysterious that's under the sea surface?

Who knows what's down there?

NARRATOR: Perhaps what lies underneath is something

that doesn't want to be found

- When you look closer at these holes, you see that around each of

them there's these small mounds of sediment.

NARRATOR: Could this be an indication that some small creature

is burrowing under the sandy surface?

- There are several marine species that are known to burrow into

the ocean floor, like box crabs.

- Probably the most dramatic of these is the male puffer fish who

creates these incredible, underwater geometric crop circles to

attract a mate.

- They do that with the continuous flapping of their fins as

they swim along the seafloor.

- But these puffer fish crop circles are way too big and don't

look anything like our deep sea holes.

- There are other animals like sea worms and garden eels that

create holes similar to the ones we're seeing here on the

Mid-Atlantic Ridge.

NARRATOR: Creatures whose burrowing behaviour are well documented.

So why don't scientists just wait to see what pops up from these

newly discovered holes?

- Because it's possible that whatever made these holes

is long gone. As in long dead.

- If that's the case, these could be what's called ichnofossils.

- Whereas traditional fossils are the preserved impression of

something that was once living, ichnofossils are the preserved

impression of an activity that this once-living thing left behind.

Like a dinosaur footprint.

NARRATOR: Or, in this case, perfectly spaced rectangular holes

dug into the sea floor for whatever reason.

- The truth is our oceans are filled with bizarre and wonderful

creatures both big and small that we've never seen before.

So we're discovering these animals for the first time.

- So with these holes, we might not understand what creature made

them or why, for the simple reason that we just haven't

discovered that creature yet.

- We've got no idea what makes these things.

We don't even know if they're made by something underneath the

surface or made by something walking along the surface.

It's a mystery, basically.

NARRATOR: Perhaps the ultimate origin and purpose of these strange

deep sea holes will forever remain a mystery.

- Our oceans make up 71% of our planet and yet there's so much about

that world that we simply don't know.

- A lot of it hasn't been explored by humans yet because you need

such specialized equipment to even get anywhere close to get that deep.

- But what we do have is this amazing technology that allows us to

scan these hidden worlds from above and start to explore their

deep sea mysteries.

NARRATOR: From a rare war relic discovered at the bottom of the

Mediterranean, to bizarre bubble patterns in a sea down under,

to a ghostly island off the coast of Japan, and curious deep sea holes

dotting the world's longest mountain range, the view from above allows

us to investigate the mysteries of our planet's ocean depths.

Subtitles by Sky Access Services