All language subtitles for Monsters.of.the.Deep.20000.Leagues.Under.the.Sea.S01E01.1080p.HDTV.H264-DARKFLiX_track4_[eng]

Deep in the ocean's dark abyss,

20,000 feet below the surface
in the freezing depths,

lurks a strange, unexplored world.

Where alien-like creatures...

...grow to terrifying sizes

and are the ruthless predators...

of the abyss.

Many look like something
from our darkest imaginations.

While some create the myths
and legends of the deep.

Weird creatures with alien ways
to hunt...

CRUNCH
..and kill.

It's said we know more about Mars
than we do our deep seas

and the strange life forms
within it.

This series will uncover
the great unknown,

come face to face with some
of the sea's most elusive creatures,

and use cutting-edge technology...

...to reveal behaviour
that has never been captured.

These are the unknown
and unseen monsters of the deep.

In this program me,
we meet the killers.

From strange
and mysterious predators

with remarkable abilities
to attract...

...and hunt prey...

They are able to produce red light
like a searchlight.

Looking for prey items.
It's so cool.

...to super sized marine reptiles...

...and the original big biters.

MECHANICAL CLANGING,
CRUNCHING

That did it.
CH UCKLES

But why does the deep sea
create these killer monsters?

CRUNCH

Out there is a cast of our planet's
most terrifying killers.

But many of them lurk so deep
below the surface

that finding them
is notoriously difficult.

Exploring the endless expanse
of the deep, dark ocean

is incredibly challenging.

And the conditions are so extreme

that the creatures
which survive down there

are unlike anything we see
at the surface.

For some of these deep sea dwellers,

there's one fish
that coming face to face with

would be their worst nightmare.

This is the anglerfish.

With an enormous mouth...

...and razor sharp teeth,

it's one of THE most iconic
deep sea killers.

The anglerfish lives at about
two kilometres below the surface

in the eternal pitch darkness.

The chances of just happening
upon prey are very slim.

So how does the anglerfish manage
to find a meal?

The answer is by harnessing
the remarkable ability

to create organic light.

It's called bioluminescence,

and it's produced
by a chemical reaction

inside a creature's body.

On land, it's rare,

but in the oceans it's used
by an astonishing three quarters

of all deep sea creatures.

Forget TikTok and Instagram,

this dazzling light show is by far

the world's most common form
of communication.

But the crafty anglerfish
has found a way

to take advantage
of bioluminescence...

THUNDER RUMBLES

...and weaponize it.

They're not exactly built
for speed...

...but what they lack
in hydrodynamics,

they make up for
with patience and ingenuity.

Sticking out of their forehead
is a narrow dorsal spine

with a glowing tip.

Which they can wave around
like a fishing rod

to attract prey in the dark.

But as they live at such depth,
they've never been seen hunting.

This is because most of life
in our oceans...

...exists at a depth
of less than 200 metres

in what's known
as the sunlight zone.

Here, the sun's rays create a warm
and bright environment.

Below that is the twilight zone,

where little to no light
filters down from above.

Deeper still,
between 1,000 and 4,000 metres

is the freezing cold, pitch black
dark abyss of the midnight zone.

So what exactly might be lurking

in this desolate abyss
for anglerfish to prey on?

The unique tank room at
London's Natural History Museum

may be able to shed some light.

Curator of fishes isjames MacLaine.

This is a spectacular specimen
of a very rare anglerfish.

Ancl you can see several
of the typical anglerfish features.

So we have the little tiny eyes.

They don't have very big eyes
at all.

Ancl this is the lure.

This is where anglerfish
keep colonies

of bioluminescent bacteria
which attracts the prey

towards this incredibly
fearsome mouth

full of vicious,
backwards-curved teeth.

It also has little batteries
of teeth on the roof of its mouth

and right in the back
of its throat as well.

So anything it grabs has very,
very little chance of escape.

Ancl this specimen
is particularly interesting

because it has grabbed something
quite significant.

It has this very big, stretchy,
elasticated stomach,

and this has swallowed something
quite considerable.

I can feel there's quite a large,
lumpy object in here.

Ancl I'm very curious to find out
what this is.

Not wanting to slice
this unique specimen open,

James is taking it
to the museum's forensic lab...

...to conduct a CT scan
with manager Agnese Lanzetti.

Similar to brain scanning machines
used in hospitals,

it takes thousands of x-rays
to build a detailed 3D image

of both the anglerfish

and the skeleton
of whatever's inside it.

This is great. It's so clear.
So this is the anglerfish.

This is what it's got
in its stomach.

If we rotate a bit,

we should be able to see
not just the teeth in its jaw,

but it's got teeth
on the roof of its mouth as well.

Yeah, there they are. There.

So it's got these quite nasty
backwards-facing fangs.

Ancl what usually happens
with predatory fish

who are attacking other fish,

they like to get them by the head
and they sort of clamp down on it

and stop the fish from breathing.

And that will kill the fish,

that makes it a lot easier
to swallow it.

So these massive eyes,

that's what would have led it
to its doom.

It would have seen the lure
of the anglerfish in the darkness

and gone over to investigate.

Ancl that would be
the last thing it saw

before it was swallowed.

In the freezing cold isolation
of the midnight zone,

two kilometres below the surface,

a hungry anglerfish is playing
a waiting game.

As an ambush predator,

it has to be ready to strike
at any moment.

In the deep ocean...
CRUNCH

...when there's an anglerfish around,

it's wise not to be afraid
of the dark,

but to be afraid of the light.

Thanks to the beautiful results
we got from the CT scan,

I think I've worked out
what the anglerfish has eaten.

The first thing I noticed
is the fish inside the anglerfish

has got these two large fins
near the back of its body

that are roughly the same size,
and they're above each other.

Ancl that is a feature
of a group of fishes

called the smooth-heads.

Ancl I believe
it's rouleina attrita,

the soft skin smooth-head,
that is inside the anglerfish.

Ancl because we have
such an amazing collection here

at the Natural History Museum,
if you think of a fish,

chances are we've probably got it
in one of our cupboards.

And sure enough,

we have some lovely specimens
of rouleina attrita here.

Ancl get one out. Let's get this one.

This is probably not too far off
the size of the fish

that's actually inside there.

So the anglerfish
has eaten something

that's almost twice as long
as itself.

It's probably like the equivalent
of us eating something like,

I don't know,
a Saint Bernard or something,

something pretty hefty.

So it's got this amazing
stretchy stomach

so it can fit really, really
quite large prey items inside.

Food doesn't come along very often
in the deep sea,

so you have to make the most
of every opportunity.

Ancl that probably would have
kept it going for a long time,

several weeks, if not longer.

So it's a supremely well-adapted
predator for its environment.

Lethal jaws are crucial
for any killer in the deep.

From a great white,
to a killer whale, to an anglerfish.

But it hasn't always been that way.

The ability to bite had to evolve
like any other predatory strategy.

And it all began with one
of the most ferocious-looking fish

ever to swim in our oceans.

Our seas are home
to countless killers.

While some, like the anglerfish,

have developed
sophisticated methods to hunt...

...others use highly-potent venom.

Higher up the food chain,
you can't beat a ferocious set...

of jaws.

The infamous bite
of the great white shark

is the most feared weapon
in the water.

But all of today's biting predators
owe their killer instincts...

...to a prehistoric pioneer.

419 million years ago,

our planet
was a very different place.

On land,
the plants were relative newcomers.

And the dinosaurs wouldn't be around
for another 200 million years,

but the oceans
were teeming with life.

This was the start
of the Devonian Period,

also known as the Age of Fishes.

Back then,
there weren't any big predators...

...certainly not
as we know them today.

But evolution was about to go
into overdrive.

Spawning a new generation
of aquatic killers, the placoderms.

What set them apart

was that they were the first fish
to develop hard, bony jaws.

Our oceans
would never be the same again.

The development of jaws
was an evolutionary game-changer,

one of the most important

in the history of life
on our planet.

All of a sudden, fish didn't just
have to be passive filter feeders

on the sea bed,
they could be active killers.

This, of course, made the sea
a much more dangerous place to be.

But placoderms also
developed protection

in the form of armoured bony plates
around their head.

But as the arms race between teeth
and arm our intensified...

...bigger, formidable, ferocious
fish-slicing monsters evolved.

And around 382 million years ago,

the biggest and baddest
of the lot, Dunkleosteus.

Measuring up to ten metres
in length,

Dunkleosteus was not only
a huge placoderm,

but also one of the world's first
top predators.

Only a few complete skulls
of this revolutionary big biter

have ever been discovered...

...near the Great Lakes
in North America.

At the Royal Belgian Institute
of Natural Sciences in Brussels...

...palaeontologist Sebastien Olive

has a cast of one of these
very rare fossilised skulls.

Here we have Dunkleosteus.

The size is quite impressive
because you have the skull there,

until there,
and after that you have the trunk.

And the head and the trunk

are connected
by very strong and powerful muscles.

When they were contracted,

it permitted a very huge opening
of the mouth.

You can see here on the upper jaws,
there are two fangs.

Ancl on the lower jaw,
you have also two fangs,

and you have a very sharp blade.

So we had an animal
with a very powerful crushing bite

to allow it to catch prey.

As the dominant predator,

Dunkleosteus would have preyed upon
other placoderms.

Which means its jaws would have
to be able to bite through

their bony arm our.

Similar behaviour has been observed

with modern day tiger sharks
hunting large marine turtles...

...crunching through their thick,
heavy shells.

Our seas have long been home
to some seriously powerful biters,

but what were those first sets
of apex predator jaws like?

This precise 3D scan of a rare,
complete Dunkleosteus skull...

...created by the Cleveland Museum
of Natural History,

could reveal clues
about how they killed their prey.

Placoderm expert Martin Brazeau
from Imperial College London

wants to use this model

to put Dunkleosteus' primitive bite
to the test.

What we have here is a very nice
three dimensional model

of the skull and shoulder
of Dunkleosteus.

All these bones
can really tell us a story

about how the jaws
of this animal functioned.

The biting force of this type of jaw
was about 4,500 newtons.

Now, to put that into perspective,
the strongest bite forces today

would be something
like a saltwater crocodile,

which is about 16,000 newtons,

or a great white shark,
which would be about 18,000 newtons.

So it's quite a bit less
in terms of force

compared to some
of these modern animals.

But that very high bite force
in a saltwater crocodile

is going to be distributed
over a much wider area.

Whereas in the case of Dunkleosteus,

the initial force
would be concentrated

on the very sharp points
at the front of the jaw.

The question is,
would that have been enough

to get through the tough
arm our plating of its prey?

The 3D model provides another clue.

At the top and bottom
of the skull,

large muscles
would have worked together

to pull the upper
and lower jaws apart...

...creating a massive gape...

...before interlocking cheek muscles
snapped it shut in a flash.

BANG

So what we're really interested
in finding out today

is what are the impacts of this
very different mode of biting

on something like a piece of bone.

To bring the jaws back to life,

Martin is enlisting the help
of Drjim Watson

at the Cranfield Impact Centre.

He's reconstructed the fangs
of Dunkleosteus

and attached them
to a mechanical press

matched to its bite force.

With a cow bone acting
as the arm our plating of its prey.

Arm in.

Three, two, one.

CRACK

That did it. Yeah.
CH UCKLES

Definitely got that fracture.

Yeah, it looks like the bone
is broken

in a kind of long fracture,

and the fangs
have gone clean through.

Obviously, the speed of closure
is quite critical

because it really tells us something

about what Dunkleosteus could do
with its jaws.

What we've seen is that Dunkleosteus

had these pointed fangs
at the front,

and they would have initiated
the puncture into the prey.

So that would have created
the weak spot

for the jaw to continue travelling
through the flesh of the prey.

So they were shearing jaws,

so they would have operated
much like scissors in a way.

A reasonable analogy
might be something like

a modern-day tiger shark,

where they gouge out
these big gobbets of flesh

from the side of their prey items.

Since the time of Dunkleosteus,

marine killers have evolved
and diversified

into weird and lethal biters
we see today.

Like the rarely seen
and eel-like frilled shark.

It usually lives 1000 metres down
in the midnight zone,

but every night it rises
to hunt in shallower waters.

Rather than just the two bony fangs
of Dunkleosteus,

it has more than 300 teeth.

And its jaws might be weak,
but it can swallow prey whole.

Its teeth act like vicious barbs

to prevent prey escaping
once they're snagged.

Its cousin, the goblin shark,

uses its jaws and teeth
very differently.

Its elongate snout,
packed with electrical receptors,

help it detect its prey

to lock on in the darkness
of the twilight zone,

hundreds of metres
below the surface.

But it means its jaws
are under its large snout,

so it attacks by catapulting
its jaws forward, alien-like,

in the blink of an eye.

But just as predators of the deep

have become
increasingly specialised,

so too have the survival strategies
of the creatures they prey upon.

The transparent skin
of the mesmerising glass octopus...

...acts like an invisibility cloak.

Predators will literally
see straight through it.

While some deep sea squid
squirt luminous ink

to create a smokescreen.

And the a toll a jellyfish

flashes like a burglar alarm
when attacked.

Down here,
getting your defensive game right...

...could mean the difference
between life and death.

But there's one unique killer
that uses light to hunt and kill

like no other in the darkness
of the midnight zone,

over 1,000 metres down in the abyss.

Life in our oceans
is a delicate balance

between finding food
to kill and eat,

while avoiding being killed
and eaten yourself.

For the very top predators,
it's all about getting more deadly.

Whilst things further down
the food chain

go to extraordinary lengths
to avoid detection.

But there's one killer in our seas

that manages to be both a predator
and as good as invisible,

the marvellously named
stoplight loose jaw.

The stoplight loose jaw

is one of the most cunning
and stealthy killers

in our ocean today.

A streamlined hunter
which prowls the darkness

of the midnight zone,

over 1,000 metres down,
in search of prey.

But how does it find its next meal
in the pitch black?

The answer is to do with light.

More specifically,
the colour of light

and how it behaves in the deep,
dark ocean.

Sunlight is made up
of all the colours of the rainbow.

When it shines down through the sea,

the colours lose their intensity
and eventually disappear entirely.

But because each colour
has a different energy level,

they disappear at different depths.

With the lowest energy red light
being the first to go.

While at the opposite end
of the rainbow,

blue light has the highest energy
and penetrates the deepest.

So blue is the best colour
to be seen in the deep sea,

and red is the best colour
if you want to disappear.

That's why so many creatures
that live in the inky depths

are bright red.

At the surface, they would stand out
like a sore thumb,

but in the deep,
red makes them almost invisible.

To explore how this works,

I've come to a lab
at the UK's home

of deep sea exploration,
the National Oceanography Centre.

So how does light function
for animals in the deep sea?

Well, this box represents
the infinite inky blackness

of our deep oceans,
and at the back is a red fish.

Now, if I add some blue light...

...which is quite common
from bioluminescence,

it actually doesn't make
that much difference.

In fact, the red fish
still blends in to its background.

However, if I switch that
to a red light,

it's a whole different story.

All of a sudden, that fish pops.

It really stands out
against its background

and would be hugely vulnerable
to a predator.

It's this unique quality
of red light

that the stoplight exploits.

Marine researcher Jethro Reading

has been studying these elusive fish
for the last two years.

Jethro, tell me about how

the magnificently named
stoplight loose jaw

uses light to its advantage.

So, it's got that name
because the stoplight loose jaws

are among a very few species of fish

that are capable of producing
red bioluminescence,

they are able to produce red light.

It's thought to use
this red bioluminescence

like a searchlight,
so it scans the water around it,

looking for prey items,
in particular fish,

and these small crustaceans,

these small red shrimps
called copepods.

So where
is that light-producing organ?

So these shores are covered
in light organs

all along the underside
that provide camouflage.

And then under these huge eyes

there's this
teardrop-shaped light organ,

and this is actually what produces
this red light.

Ancl what's really clever about it

is that a lot of the prey items
at these depths,

because there's so little
red light around,

have actually lost the ability
to see red light.

Which means that they can be
snuck up on by loose jaw

without them having any idea.

It is like some kind
of Marvel superhero, isn't it?

With lasers under its eyes,

just shining on stuff around
to find it.

It's amazing. It's so cool.

Being able to both see
and produce red light

gives the stoplight loose jaw

a phenomenal advantage
over its prey.

It's like a sniper
with night vision goggles,

illuminating its target
like a beacon,

while its prey remains
completely oblivious

to the danger it's in.

So that's the stoplight part
of things. Mm.

What about the loose jaw area
of its name?

How does that function?

So, I mean, we've got a model
of a stoplight loose jaw here.

If we animate this model,

and you can see that this jaw
is massive,

it's approximately 30%
of the fish's total length.

Ancl it can open to a huge extent.

And it does this by
some very clever articulations.

So there's an extra hinge
up here behind the head.

Ancl this is actually a really,
like, quite freaky adaptation.

This is where it gets
this name Loose jaw.

The jaw is phenomenal and it's vast.

But there's one thing it's missing.

And you look at the underside
of the jaw, it's just a gaping hole.

It's missing this bit, isn't it?
Yeah, it's missing all the membrane.

Missing all the flesh
underneath the jaw. Yeah.

So members of the loose jaw subfamily
completely lack the membrane,

the skin on the underside
of their mouth.

Instead, they just have this one
elastic exposed muscle

connecting the jaw to the back,

and all the other soft tissue
is absent.

This enables the jaw to move
pretty rapidly and very efficiently.

It can close
in about a tenth of a second.

It's got these huge, huge fangs

that basically are able
to just pierce

any prey item they come across.

Ancl more importantly,

these teeth actually have
a crystalline structure

which makes them translucent,
makes them transparent,

makes them just completely disappear
into the water.

Camouflaged teeth.
Yeah.

That is going the extra step,
isn't it?

You've got to just try
and stay hidden

for as long as possible,

until you are close enough
to get your jaw out

and strike your prey.

Very cool.

As food is such a precious commodity
in the deep,

when going in for the kill,

it pays not just to have
a loose jaw,

but also a fast jaw.

The stoplight can open and close
its mouth quickly,

because its unique hollow lower jaw
reduces drag through the water.

And many other killers in the ocean

use the fast opening of their jaws
as a potent weapon.

So opening the mouth really wide
allows you to take in big prey,

and closing the mouth fast

can apply greater force
and pressure.

But why is it also important
to open the mouth fast?

Well, let's imagine

that this little bit
of chewing gum here is a fish,

and my hands are going to act
as the jaws of a predatory fish.

It's all well and good
closing them fast.

But if that's all you do,
then this is the result.

The fish gets driven further away

because the jaws closing creates
a wake or turbulence,

driving water out of the mouth

and pushing the fish away
from the teeth and the jaws.

Whereas if you can open
that mouth really quickly,

then it drags water and the fish in,
like this.

So I guess
I am opening my hands there

at about half a second.

There are fish alive today
that can do it in a millisecond.

Highly specialised suction feeders

can open their mouths
at such lightning speeds

that we need super slo-mo cameras
to see it properly.

As they rapidly increase the size
of their mouths to feed,

a vacuum is created inside.

Water immediately gets sucked in

along with any unlucky fish
caught in the firing line.

It's such an effective
and efficient feeding method

that almost all fish use suction,
from minnows to monsters.

But many of the ocean's
most successful killers

aren't fish at all.

The ultimate predator in our oceans
today is the orca.

The killer whale.

And that is a mammal
which came from the land.

They weren't the first air breathers
to return to the sea.

So how did air-breathing animals

not only adapt
to an ocean environment,

but become the ultimate killers
of killers?

When we think of killers
in the seas of today,

we generally think of sharks.

Yet today's most formidable
ocean killers are not sharks,

not even the great white shark...

...but are orcas, the killer whale.

This is an animal
that is efficient...

...ruthless...

...intelligent and deadly.

They hunt and kill on their own
or as a group.

And on occasion, kill other whales.

And even great white sharks.

They are unrivalled as killers
in the seas of today.

Yet these air breathing assassins
evolved over millions of years

from a land-living mammal.

Just what is it that draws killers
back to the seas?

The surprising answer can be found
at the National Oceanography Centre.

This lab holds a part of the answer

because these jars
are full of plankton.

These here are phytoplankton.

That's essentially plants.

When it's blooming,
you get this pea-soupy green colour.

The abundance
of this extraordinary plankton

is the greatest source
of food on Earth.

Phytoplankton is food
for this...

...zooplankton,
which is microscopic animals.

We can get a look
at those under the microscope.

You should see lots of tiny
little critters swimming around.

And these zooplankton are eaten
by slightly bigger fish,

and they are eaten by bigger fish,
and bigger fish, and bigger fish.

This plankton provides
the foundations

for the most dynamic and productive
food chain on the planet.

And this is what draws
air-breathing animals

back to the sea.

A process that takes evolution
millions of years.

But the first air-breathing killers
to return to the sea...

...were reptiles.

And they did it
millions of years earlier.

A recent fossil discovery reveals
they evolved into killing machines

every bit as deadly
as today's killer whale.

But what is it
about the evolutionary process

that turns a land predator
into a killer of the deep?

THESE 8T3 mosasaurs.

And the most recent mosasaur,
discovered in 2022,

is called Thalassotitan,
which means giant of the seas.

It's one of the all-time killers
of the deep.

Marc Jones
of the Natural History Museum

is a leading expert on mosasaurs.

Mosasaurs are a diverse group
of reptiles

and have been found
all over the world.

The largest mosasaurs
could be up to 17 metres long.

They have all the attributes
of efficient killers.

You can see that this skull
is triangular in shape,

which gives it a streamlined aspect,

so it would be able to move
through water more easily,

but also allowed the animal
to attack and eat large prey.

They were so successful
they dominated the deep,

much like killer whales do today.

Here you can see the jaws
of a large mosasaur.

So these are the sort of jaws
you'd expect for an animal

that was attacking
other large marine reptiles.

So you have these large teeth.

The length of the tooth

would have helped
penetrate large prey.

Ancl this increased the likelihood

that they would have reached
internal organs,

causing huge amounts of damage,
huge amounts of blood loss,

separating flesh from bone,
even bone from bone.

The mosasaur teeth are formidable
and have a familiar look to them.

So this is a tooth
of a killer whale,

and if I hold it
to the mosasaur tooth,

you can see that there are
broad similarities.

So you have this robust base
and then this stout crown

and this subtle curvature.

Teeth are key to understanding
how and what animals hunt.

And evolution shapes teeth
to do the same job.

The fact that killer whales today

hunt other whales
and other vertebrate animals

indicates that mosasaurs

also attacked and ate
other vertebrate prey.

An adult mosasaur
could eat pretty much anything.

It would have been able to tackle
the turtles it lived with,

the sharks, the large fish,

and the other marine reptiles
that were in its environment.

Alongside the fossil bones
of Thalassotitan,

discovered in 2022,

were semi-digested bones
of another mosasaur.

Thalassotitan
is a killer of killers...

...and it's smart.

Bite marks found on mosasaurs skulls
reveal it went for the head,

preventing its prey from biting back
and drowning it.

CRACKING AND CRUNCHING

Smart, ruthless, and deadly.

We know that mosasaurs evolved
from land-living lizards.

But how do you get
from something like that

to a colossal monster of the deep?

Today's marine iguana is unique
to the Galapagos Islands.

It's a lizard that spends
much of its time in the sea.

They can spend
up to an hour underwater.

Over time,

they've evolved some adaptations
to an aquatic lifestyle.

Their tails are flattened
to help them swim,

their feet are partially webbed,

and their bones are more dense
to help them dive.

While the marine iguana
has some characteristics

that allow it to spend time
in the sea, it's not fully aquatic.

Thalassotitan
is more closely related

to the Komodo dragon, a predator.

So how could a land-based reptile
like the Komodo evolve

to become a ferocious killer
of the deep,

but unlike the marine iguana,

is entirely adapted
to life in the ocean?

Evolutionary biologist
Dr Jennifer Hoyal Cuthill

from the University of Essex

can shed light
on how the Komodo dragon

could evolve to become
an ocean killer.

If Komodo dragons were
to re-enter the ocean,

they may have to evolve
in different ways.

We can think about how their body
might change

to improve their swimming ability
in the ocean.

Komodo dragons
are already good swimmers.

But to be efficient ocean killers,

they would need to adapt
their swimming style.

They use an undulating motion
of the body,

so we would see
a stiffening of the body,

and then the evolution of webbing
between the toes.

Then progressively producing
flippers for swimming,

almost like flying
through the water.

The tail increasing elongation
to form a tail fin,

allowing them
to move through the water

with tail-driven propulsion,
similar to mosasaurs.

The Komodo dragon
has an amazing sense of smell

that might potentially be helpful,
as it is for sharks, for example,

to find prey from a distance.

That might be something
that would be kept by evolution

on a re-entry into the oceans.

Evolution refines and reshapes
an animal's body

to enable it to live in the sea,

adapting it over millions of years

to make it more efficient
in its new world.

The main reason
animals are drawn back to the sea

time and time again

is because the oceans
are the richest food sources

on the planet.

And when mosasaurs became extinct,

that paved the way
for a new generation

of air-breathing animals to rise
to the top of the food chain.

Culminating in the orca...

...to claim the title

of the ultimate killer
in the seas of today.

Our oceans are rich
with opportunities

to thrive and survive,

both the creatures
that were drawn back

and for those that never left.

They may be vast, dark, and hostile,
but they're also an engine,

driving the evolution
of our most formidable killers.

Unlike on land, the ocean is home
to few large herbivores.

Virtually the whole ecosystem
is made up of killers.

Of animals eating other animals.

From the earliest killers
with primitive, but powerful jaws,

and those that use light
not just as a lure...

...but to seek and kill prey.

And land dwellers
that became giant ocean predators.

It's an unforgiving place
where only the strongest survive.

Because the rule of life
is eat or be eaten.

Next time, we go in search

of the ocean's weird
and wonderful giants.

From the biggest monsters
lurking in the deep

to giants that live longer
than any other animal.

From ferocious super predators

to enigmatic monsters
that haunt our subconscious.

Oceans continually create
the most immense giants

the world has ever seen.