Where the last sliver of land disappears
behind the horizon,
a vast, liquid wilderness stretches endlessly
in all directions.
Here lie more than 300 million cubic miles of water.
The earth's largest environment.
Scattered across its shifting expanse
are rich shoals of mackerel, sardines,
anchovies,
and, hot on their trail,
the ocean's swiftest and most powerful predators.
This is a hunter's world,
and competition is fierce.
For prey, life is all about vigilance, speed,
and cheating death for one more day.
Or not.
Remarkably, for animal life,
the open ocean is a virtual desert.
Just 10% of the world's marine creatures live here.
The deep blue is all but empty and eerily huge.
The scale hits you right way when you're out in the big blue,
out in the open ocean.
You know, at first, there's nothing to glom on to.
You don't see a reef, a piece of kelp.
Nothing. You're in deep blue space.
You start to see things materializing out of the blue
from tiny, tiny little jewel-like forms
to, if you're really lucky, the super big guys.
A pod of Pacific spotted dolphin
on the move to where prey abounds.
And they can get there fast,
reaching speeds of up to 25 miles per hour.
They'll travel as much as 100 miles a day
and have a little fun along the way.
With food now in range, the dolphins rely on echolocation.
They emit high- and low-frequency clicks
which bounce off objects that may be out of sight.
It is believed that the clicks' echo
gives the dolphins a 3-D map of their surroundings
and the creatures swimming through it.
Right now, mackerel appear on their map.
Alerted by the dolphins' clicks,
the shoal of mackerel pull closer together
into what biologists call a bait ball.
Some believe this tactic evolved to trick predators
into thinking that the shoal is actually one large animal.
As the mackerel whirl,
the dolphins pick off the stragglers.
Vibrations from the shoal alert another carnivore.
A sailfish.
Clocked at 70 miles per hour,
it's one of the ocean's fastest predators.
With sail at full mast,
it herds the fish into an even tighter bowl.
The sailfish brings another ingenious weapon to the hunt.
Once excited, it glows with ultraviolet blue stripes.
Mackerel eyes are especially sensitive to ultraviolet light.
They may become disoriented by the fast-moving stripes,
making them easy prey.
The frenzy was also electrifying to producer Andy Byatt.
It's an enormous buzz being there
because unlike land filming,
the only way to film it
is to be right there in the middle of it all.
And you really are right there in the middle of it all.
You have a sailfish going... Swimming that close to you.
With its quarry in sight,
the hunter lowers its sail and hits the throttle.
Far below, a blue shark returns from hunting in deeper waters
to warm itself near the surface.
As it ascends,
the shark smells the oils and proteins shed into the water
by the panicked mackerel.
The scent trail leads
both the shark and its companion pilot fish
towards a few scraps left over from the sailfish's feast.
Across the open ocean,
predators and prey are locked
in a three-dimensional game of hide-and-seek
played out over immense distances.
To survive, they must constantly travel.
More than 25 feet from one fin tip to the other,
a manta ray makes a leisurely journey
to an island feeding ground.
Two remora fish hitch a ride.
They get free transport
and feed on their host's leftovers.
The manta ray's destination is the edge of a Pacific island.
3,000 miles from the nearest continent.
Here surgeon fish have begun to spawn.
As they perform their nuptial dances,
they discharge clouds of eggs and sperm into the water.
A delicacy to the manta rays.
As mantas swim, lobes on either side of their heads
direct the fish spawn into their mouths.
Inside, finger like projections capture food from the water
as it's strained through the manta's gills.
Within an hour, the rays have had their fill.
And the surviving eggs, now fertilized,
will begin a journey of their own,
joining the multitudes of larvae and other microscopic creatures
adrift in the open ocean.
These are the eggs of yellow fin tuna.
If the hatchlings survive,
it'll take two years for them to reach adulthood.
In three years,
they could be six feet long and weigh over 400 pounds.
But against the predators of the deep,
the odds of a hatchling surviving
are just one in a million.
Fertilized yellow fin tuna eggs drift on the open ocean,
attracting hungry storm petrels.
Theirs is an elegant dance of death.
Facing the wind, the birds hover,
picking out eggs that float near the surface.
These newly emerged tunas are smaller than houseflies,
and although they can swim, they're still very vulnerable.
It may be many weeks
before they can propel themselves strongly enough
to make any headway in the ocean or flee predators.
And the danger doesn't end when the sun goes down.
After dark, drifting hunters rise from the depths
to attack the hatchling tunas.
Shimmering sea gooseberries unfurl sticky, net-like webs.
The perfect trap for tiny fish.
And though comb jellyfish may look delicate and beautiful,
they're true carnivores.
As the morning light pierces the darkness,
most of these thin-skinned predators
retreat back to the safety of the cooler, dimmer depths.
And the surviving tuna hatchlings are picked up
by a powerful current.
The open ocean is never still.
Vast current systems, like enormous rivers,
carry the hatchlings around the ocean basins.
Immense schools of fish, like these sardines,
travel along the currents,
seeking spots where their food, plankton,
is most plentiful.
But in this treacherous realm,
the hunters can quickly become the hunted.
Voracious predators,
striped marlin can grow to 10 feet long
and weigh 500 pounds.
The fish marlin hunt are normally widely scattered,
but sometimes their prey, like these sardines,
gather in dense shoals.
Rick Rosenthal found that sharing the water
with such a single-minded predator can be unnerving.
Do we expect the marlin to get out of our way,
swimming at 50 miles an hour, mouth open to eat?
We're just hoping that it'll glance off
or swim to the side of us.
Most of the time, that happens,
but, at other times, I've had the camera hit.
I've had the fish take my light meter off on my camera.
This feast may last for over an hour.
Time enough for other hunters to reach the scene.
Among them, one of the most spectacular giants of the sea
Sardines, some of the smallest creatures in the sea,
have attracted one of the largest.
A 40-foot, 20-ton sei whale.
I was just floating along, minding my own business.
All of a sudden, this whale came up
and just ate right next to me
and ate the whole shoal of fish.
All I could do was pull the trigger just on a reflex action
and went, you know, 'Holy you-know-what.'
It clamps down over the remaining bait ball,
then filters out the water through its baleen,
a strainer of comb-like plates attached to its upper jaw.
For the sardines, there's simply no defence
against one of the largest mouths in the ocean.
It was the very last day
of 3,000 days of filming for 'Blue Planet.'
It was the very last roll of film.
The most extraordinary thing about it
is there's a shot where the tail flick
comes very close to camera.
What people don't perhaps appreciate
is that's how close it was.
Soon the only sign that the sardines ever existed
are scales sinking down into the abyss.
With so much of the open ocean devoid of life,
animals at the top of the food chain
need to travel tremendous distances
to find food and places to breed.
Solitary voyagers, olive Ridley turtles
can travel thousands of miles a year
between their feeding grounds and their nesting beaches.
Blue fin tuna use their muscles to warm their blood
to keep them warmer than the surrounding water.
This allows them to travel thousands of miles away
from their tropical spawning grounds
to hunt in cold seas where the food supply is richest.
But not all ocean dwellers are long-distance swimmers.
Some just go with the flow, like this jelly.
Or this seafaring crab that spends much of its life afloat.
Like flying carpets, a flock of golden cow nose rays
gathers together for a perfectly synchronized courtship dance.
June in the Atlantic Ocean.
These pilot whales are on their way
to their breeding grounds in the Mediterranean.
Pilot whales normally hunt in small family groups.
But in midsummer, they start assembling
into larger and larger social bands.
The males vie for the females' attention.
Affectionately rubbing up against them
as the herd floats lazily along.
With a ratio of eight breeding females for every suitor,
the males have their work cut out for them.
As the weeks pass,
this group behaviour will become overtly sexual.
But for now, it's just flirting in the sun.
At the other end of the size scale,
flying fish spend their whole lives
on the run across the high seas.
Instead of scattering their eggs in the open water,
they lay their clutches on pieces of flotsam
like this palm frond,
which will serve as a life raft for their developing offspring.
Any floating debris might become a shelter for young fish.
And in the open ocean,
there's intense competition for real estate,
no matter how humble the abode.
Trigger fish drift from place to place under shelter,
using flotsam as a home base from which to search for food.
And when they think they've found prey,
the hungry fish will band together to attack.
Even a diver.
They're voracious.
It's like little piranhas out there.
They've been waiting a long time.
You're floating along for all day, all week, all month.
Hey, a diver looks pretty good at that time,
especially one without a wet suit on.
We've had to get out of the water,
literally run out of the water,
'cause the trigger fish are biting at us so much.
Out here,
even discarded netting can provide valuable shelter.
So in an ironic twist,
a trawl line meant to catch fish ends up as their refuge.
Many fish and small larvae
will congregate around flotsam,
but that is not to say that 'Flotsam's great.'
Let's chuck more out there,'
because the flip side of the coin
is that tiny fish to all the way up the chain to whales,
things will get entrapped and drown.
Once they're entrapped, that's it. History.
Man-made debris is, at best, a mixed blessing.
This immense sunfish prefers a seaweed hideaway
for a rendezvous that may make your skin crawl.
The mola mola, or ocean sunfish,
can grow up to 13 feet long
and weigh as much as 4,000 pounds.
But their soft, fleshy skin is, well, nasty.
When you look at that animal, it's almost a horror show,
not in terms of its beauty and its unusualness,
but it's loaded with parasites.
So I don't think you want to go to a sushi restaurant
that's serving mola mola.
Here amidst the floating kelp,
the sunfish seeks out the company of a nibbler
that finds its parasites delectable.
The half-moon fish.
The sunfish turn their heads towards the surface,
an invitation to their team of personal hygienists
to chow down.
It's a stomach-turning relationship.
The sunfish languidly floats
as the hungry half-moons try and strip off all the parasites.
If the half-moon team can't finish the job,
the sunfish turns to a real specialist.
A seagull pausing to rest on the floating kelp.
The sunfish approaches the surface and turns on its side.
The gull investigates,
then pecks the sunfish's skin,
stripping off even the most determined parasites.
Finally, relief.
These flotsam sanctuaries are only temporary havens.
As the seaweed rots, it loses its buoyancy.
Yet the open ocean does offer permanent shelter.
The Pacific Ocean is peppered with over 23,000 islands
and countless sea mounts,
submerged mountains whose summits never break the surface.
Sea mounts are promising feeding grounds
for young yellow fin tuna,
which grow at an astonishing rate.
They grow unbelievably rapidly
from this tiny, tiny egg, grain-of-salt size,
to, if they're allowed to,
an adulthood of 100 kilos.
Big, big fish.
Now more than six months old,
they're big enough to gorge on smaller fry.
And the sea mount attracts them in great numbers.
Marine life is plentiful here
because of the deep-sea currents.
As these cold, rich waters sweep along the ocean floor,
they're deflected up the sea mount's towering walls...
bringing nutrients and plankton to the surface.
Thousands of reef fish take up permanent residence here,
feeding where the currents are strongest
and the plankton most dense.
Where the cold water mixes
with warmer water at the surface,
there's a strange shimmering effect.
When currents come together,
particularly warm- and cold-water currents,
those edges, those fronts, as we call them,
those are usually the hot spots.
Hot spots are where we find the apex, the high-end animals,
the big predators, the whales, dolphins, sharks, marlin, tunas.
So we hunt those, and those animals hunt those as well.
Giants come here from the open ocean,
like hammerhead sharks.
During the day, they circle the sea mount,
hunting for small fish at the reef's edges.
But not to eat them.
Like the sunfish, they're desperately searching
for a cleaning crew to relieve them of their parasites.
White-tip sharks gather here, too.
They do eat reef fish.
But only at night.
During the day, they prefer to take it easy
and let the cleaners do their work.
Ocean mounts are among the busiest outposts
in the open sea.
A few times a year,
seasonal changes bring exceptionally rich waters here,
creating a virtual soup of plankton.
During these incredible surges,
fish gather in astonishing numbers.
In the blink of an eye, predators become prey
and the young yellow fin tuna are tested like never before.
Not far from the nutrient-rich waters of the mid ocean sea mount,
a shoal of anchovies has strayed up near the surface.
They can already feel the vibrations
of fast-approaching predators.
Swimming quickly, the anchovies form a whirling shoal.
So the big question becomes,
why would fish group together like that,
that makes them more vulnerable to predators feeding on them,
piling on them?
And the only answer we have
is their sensory system, their nervous system is confused.
They're jammed. It's like a computer blowing up.
I don't think they deliberately want to do it.
They don't have another option,
and if they did have another option, they'd split.
They'd swim to the bottom.
They'd get out of that situation.
At first, the giant swirling mass
seems to daunt the predators.
But not for long.
Bonita arrive and launch the first attack.
Still the shoal holds together.
Now it's time for the young yellow fin tuna to move in.
The force of this attack is so great
that the main bait ball starts to unravel.
Rick Rosenthal is one of a handful of people
who've seen the frenzy from the inside.
At times, you know, it's like lights out.
When the sardines see you, they're running for cover,
and they cover you up.
You don't know then what predators are swimming through
that dark bait ball.
That ball is moving. The shoal is moving.
It's being pushed around and eaten up.
I've seen a shoal of fish
the size of, say, an Olympic swimming pool
being eaten up within minutes
and taken down to a basketball size by predators.
To survive in the open ocean,
the young tuna have to learn to get food
when the getting's good.
Soon, they learn to follow some of the best hunters around.
Spinner dolphins are aptly named
for their incredible acrobatics.
They can make as many as seven complete rotations
before plunging back into the ocean.
Since the hunting has been good,
many hundreds have gathered together
in this frolicking super pod.
So we started picking up on particular groups
or family groups of dolphins
and following those animals
and letting those animals, those groups, build up in numbers
till sometimes they got together in a super pod,
where, particularly around noon, 2:00 in the afternoon,
you might have been following, during the morning,
10, 15, 20, 30, 50 animals.
But by noon, hundreds of animals have come together.
Their high intelligence
and advanced sonar system
make dolphins superior hunters.
For that reason, they're regularly followed
by opportunistic adolescent yellow fin tunas.
But with dolphin pods reaching speeds of 20 miles an hour,
only adult tuna in their second or third year of life
have the stamina to keep up.
But the youngsters do the best they can, for good reason.
They follow the dolphin because...
I suspect this is happening...
their chance of finding prey with something that's got
this really high-attuned echolocation system
is greater than their chance of finding prey on their own.
These common dolphins are on the move, too.
In summer, the North Atlantic waters are beginning to warm
and the hunting is good.
By June, predators from southern waters
head towards the Azores,
an island chain 900 miles off the coast of Portugal.
In the open ocean,
there's seldom enough prey in any one place
to feed such numbers.
So small groups leave the super pod
and set off on hunting expeditions.
This group will be away from the main herd for several hours.
Soon they'll join a spectacular feeding frenzy
rarely seen in the open ocean.
A dolphin hunting party is nearing the Azores,
an archipelago in the middle of the Atlantic Ocean.
Other hunters are already here.
Cory's shear waters.
Half a million of these birds breed in the Azores every year
and scour the nearby ocean for food.
Now, with virtually no wind,
they sit out the calm,
riding the gentle swells,
conserving energy.
The wide variety of hunters gathering is an ominous signal.
Something big is brewing.
By mid-afternoon,
the dolphins are starting to hunt in earnest...
using their sonar to detect prey in the water below.
As the sea breezes pick up,
the shear waters take to the air once more.
Below, the dolphins are onto something.
Working together, they drive a shoal of small mackerel
up towards the surface.
The shear waters crowd the skies above,
following the dolphins' every turn.
The mackerel are still a ways down.
But when the bait fish near the surface,
the shear waters make their move.
Incredibly, they can plunge several stories
down into the ocean.
With the dolphins now cutting off the escape route from below,
both groups of predators gorge themselves.
Soon, the diving birds outnumber the dolphins
and drive them away.
But another squadron of hunters arrives to replace the dolphins.
Adult yellow fin tuna.
Marine biologist-turned- film-maker Mike deGruy
has come to admire this powerful predator.
They're fast, big, incredibly sleek animals
that are beautiful to see underwater.
You look at a yellow fin tuna,
you're now looking at what I consider
the perfect fusiform design.
These tuna are giants, six feet long,
and they're heading directly for the bait ball.
They're clever.
They know how to find food
without having to really look for it.
They find schools of dolphin,
follow the dolphins to where the dolphins are feeding,
and then they out swim everybody,
and they can go darting through bait balls of fish
at speeds that are astounding.
I'll tell you one thing.
You do not want to get between a yellow fin tuna and its prey.
If you got hit by one of those fish,
it would literally knock you out.
Despite the arrival of these formidable fish,
the shear waters continue their attack, unfazed.
That Azorean sequence was the Super Bowl for me
because all those groups of animals were together,
dolphins and diving birds and tunas,
and the water was beautiful.
Nobody was around, and we started working that action,
and it built and it built to a beehive.
Because the scene is so overwhelming,
to see all those amazing animals come together,
it's everything you can do to hold focus.
Eventually, the tuna move on,
leaving the shear waters to battle among themselves.
When the predators move away,
the surviving mackerel swim into the depths toward safety.
The shear waters follow them down
to the very limit of their breath-holding ability.
Perhaps as deep as 50 feet.
If you read the books about sea bird biology,
Cory's shear waters aren't supposed to dive
as deep as we were filming them.
But when I'm down 40, 50, 60 feet down with the camera
and I see a Cory's shear water swimming or flying by me,
then I know they are capable of doing that.
And groups of them.
With those elegant, long wings,
they're passing you by, it looks like space.
They look like space travellers going by you, saucers.
It's one of the high points of any marine biologist's life,
to see that, to record new behaviour,
and bring things back that scientists hadn't seen before.
We know so little about the vast,
blue space of the open ocean.
Only a small part of this liquid desert has been explored.
So many treasures yet to be discovered.
I really hope that people understand
that there are creatures out there so special
that it's really worth trying to do something
to make sure that they are still there
50, 100, 1,000 years from now.
There are signs that, for some,
time may be running out.
When we started filming 'Blue Planet,'
compared to today,
the shark populations have plummeted.
What's the reason for that?
Overfishing, intense fishing for their fins.
And so about every shark has a bounty on them,
and the sharks are being removed by the tens of thousands
out of every hot spot in the ocean.
Sharks don't reproduce that quickly to come back,
so we're not seeing them as part of the system anymore.
They're just not out there.
For those that persist,
despite the changing times, life will go on.
However good or bad a feeding season may be,
as winter approaches,
the temperature of these waters will drop by a few degrees,
and the hunters will move on as they always do,
searching for the next pulse of life
in the distant reaches of the open ocean.
100 yards!
It's getting a little tight.
Your motivation in recording feeding frenzies going on
and special things is first get the shot.
Get in the water and go for it.
There's no telephoto lenses.
We're not zooming in.
The only zooming we do is with our swim fins.
The frenzy in a bait ball is totally nuts.
It's off the chart.
There's so much eating,
so many bodies piled in there, swimming fast,
and there's animals in there
with swords on the end of their noses
swimming at 50 miles an hour in and out of the bait ball.
And you just better hope that you're not in the way.
We were down to the last shoot of the whole series.
We were filming off Mexico,
and we were filming striped marlin.
All of a sudden, this whale came up
and just ate right next to me and ate the whole shoal of fish.
Come up again!
Dougie, where the hell are you? Get going.
To see a whale feed underwater is a remarkable thing.
It's very rare.
That wasn't in the script.
And when things like that happen,
sometimes that's better than a movie.
I have my whale fingers on.
That was just sweet!