Here in Britain and Ireland, we have some of the richest seas in Europe.
Our varied coastline, if you include all the many offshore islands,
is over 22,000 miles long,
and none of us live more than 70 miles away from the sea.
Yet few of us have seen the wonders beyond the beach
and beneath the waves.
In this episode, we will take you
from the most southerly point of the
United Kingdom to the furthest north,
to explain why our seas can be so productive
and reveal the threats that they face today.
Every winter, a warm ocean current, the gulf stream,
drives huge storms across the Atlantic...
...away from the Caribbean and straight towards our shores.
There, every winter, they batter the west coasts of our islands.
Waves with energy built up across an entire ocean
are hurled at our coasts.
Walls of water more than ten metres tall
crash repeatedly onto the rocks.
And as the water at depth is churned,
it brings nutrients up towards the surface.
These nutrients, combined with the warmth of the gulf stream,
are the reason why marine life here proliferates
with such extraordinary richness and variety.
Each year, in autumn,
evidence of this marine abundance appears on land.
13,000 grey seals haul out on Blakeney Point in Norfolk.
It's the largest seal colony in England.
Females, having spent most of the year feeding in our rich waters,
are preparing to produce their young.
Newly born, the pups are helpless...
...and for their first few weeks, entirely dependent on their mothers.
Seal milk is more than 50% fat...
...and the pups put on two kilos a day.
At first, parent and pup are inseparable.
But then, after a few days, the youngsters start to explore.
Other females don't tolerate the appearance
of unrelated pups on their patch.
Posing an even greater threat than the females...
...are the males.
Three metres long and weighing 350 kilos...
...they have come here to mate.
They know that soon after the pups are born,
the females will become sexually receptive once again.
This big male tries to control all the females
on this stretch of the beach.
But he has a rival.
The big male warns off the challenger,
but the intruder takes no notice.
There's only one way to settle this.
Violence.
When the males fight,
they take no notice of any pup that gets in their way.
The pup's mother intervenes...
...allowing her pup to wriggle away.
Finally, the battle turns.
The intruder starts to retreat towards the sea.
Now, the smaller males join the chase.
The big male has retained his right to mate.
Despite these battles, Blakeney Point still provides the pups
with an excellent start in life.
5,000 are born here each year.
A remarkable 40% of the world population of grey seals
lives around the British Isles.
Impressive evidence of the richness of our seas.
Beneath the surface, that wealth is very evident.
Cold, nutrient-rich currents from the north
mingle with the warm waters of the gulf stream,
and support an astonishing variety of plants and animals.
There are more than 10,000 different species here.
The effect of the gulf stream is felt most keenly
at our southernmost point, around the Isles of Scilly.
Here grows one of the biggest stretches of seagrass
to be found anywhere in British and Irish waters.
Seagrass is important globally because it collects carbon
up to 35 times faster than a tropical rainforest.
But we have lost nearly 90% of our seagrass,
mainly because of pollution and disturbance of the seabed.
Nonetheless, these marine meadows
are home to a wide variety of small animals.
Including this perhaps somewhat surprising one.
A spiny seahorse.
One of just two species of seahorse that live in our waters.
They thrive in the warmth brought by the gulf stream.
The seagrass provides them
with the seclusion they prefer for their courtship.
A crucial part of their underwater dance
involves a gentle entwining of their tails.
It's behaviour you might think to be more typical
of the warm, balmy waters of the Mediterranean.
And there is another creature
that is also more usually found in warmer waters.
The common cuttlefish.
It's the most northerly of all cuttlefish species.
This pregnant female, about the size of a rugby football,
is being guarded by a male as she prepares to lay her eggs.
First, she cleans her chosen site
by squirting jets of water over the seaweed.
Several dozen black eggs are already here,
having been laid the previous day.
And now she adds more...
...one by one, until there are up to 3,000 or so.
A month later...
...during the night, the eggs start to hatch.
A perfectly formed baby cuttlefish, no larger than a pea.
Within a few weeks,
a male has grown to a length of around six centimetres
and is already a stealthy hunter.
His eyesight is so sensitive that he's able to hunt by moonlight.
But when the moon disappears...
...even he cannot see
and the darkness usually brings hunting to an end.
But on just a few nights each year...
...something extraordinary happens.
Tiny light-producing algae create vast clouds of bioluminescence.
They're stimulated to switch on by any sudden movement in the water.
Even the slight swirl produced by a tiny crab as it breathes
has an effect.
The hunter must move very smoothly,
to avoid creating a light show of his own.
The light of the algae has enabled it to see its prey
and so hunt throughout the night.
A year later, the cuttlefish are fully grown
and this male is now looking for a female.
But the traditional breeding site is empty.
The cuttlefish that gathered here to mate...
...have been caught in a fishing pot.
They may be among the most intelligent animals in the sea...
...but they've been fooled by a simple trap.
And once in it, there is no escape.
The male outside spots a possible mate.
But he can't reach her.
Our cuttlefish population can tolerate some loss to fishing,
but surely we shouldn't put pots where they habitually breed,
and prevent them from producing their next generation
Away from the coast, the seabed may seem barren and lifeless.
But looks can be deceptive.
This muddy seafloor is rich in bacteria and algae
and provides food for one animal in particular.
A slow-moving creature that can grow up to a length of six centimetres.
The royal flush sea slug.
Thousands graze the seafloor here.
But with so much competition for the same food,
supplies eventually run out.
And the sea slugs have to move on...
...in their own strange way.
They flap their wing-like mantles and rise up from the seabed.
Drifting on the slow current, they can travel for miles.
This extraordinary mass migration has never been filmed before.
Eventually, they reach new feeding grounds.
And now they can start hoovering the seabed once more.
As spring turns to summer,
another very different migration begins all along the south coast,
and for a very different reason.
A young female spider crab.
She is searching these sandy plains for others of her own kind.
Spider crabs are normally solitary,
but now, in the summer, they start to assemble into groups.
And then, when there are enough of them, they start to travel.
Together, they journey for miles across the seabed,
all heading in the same direction.
Groups join together
and the travellers become one great horde, several-thousand strong.
They are about to face the most dangerous time of their lives.
They have outgrown their hard shells and must now escape from them.
A new shell is expandable,
but it remains soft for several hours
and until it hardens, its owner has no defence.
That is why they've made this journey together.
There is safety in numbers.
Ocean currents are one reason why our waters are so rich.
Another is the exceptional size of our tides.
Vast amounts of water
are continuously transported around our islands
by these powerful currents.
The third biggest tidal rise and fall on the planet
occurs in the estuary of the River Severn.
From low tide,
the sea level rises by as much as the height of a five-storey building
and then falls again, twice every day.
These huge transformations churn-up the nutrients
and replenish the mudflats.
Further north, on the west coast of Scotland,
the power of our tides creates another great spectacle.
The Corryvreckan whirlpool.
25 metres across.
It's the third largest whirlpool in the world.
These powerful tidal currents mix-up the water,
constantly bringing nutrients from the depths up to the surface layers.
And the influence of the tides can extend right down to the seafloor.
The animals down here thrive in these ever-moving currents.
Every square inch is bursting with life.
The flowing water brings a never-ending supply of food.
Brittle stars and sea cucumbers compete to collect all they can.
So many creatures inevitably attracts predators.
The seven-armed starfish - half a metre across.
The brittle stars do their best to get out of their way.
The huge starfish feel for their prey
using hundreds of sensitive tubed feet
that line the underside of their arms.
Yet, not every animal they encounter tries to escape.
This hermit crab, with its powerful claws,
is well able to defend itself.
Finally, the persistent starfish find what they're looking for.
A queen scallop.
Its lines of simple black eyes are able to detect fast-moving threats.
But the starfish moves quite slowly...
...and the scallop doesn't notice.
Only when the scallop feels the predator's probing feet,
does it react.
It swims away by clapping together the two parts of its shell.
It's a surprisingly effective technique,
and with luck will carry the scallop to safety.
But scallops don't have a strong sense of direction...
...and the starfish just keep coming.
The starfish first pulls the scallop shell apart
and then inserts its extendable stomach
to digest the scallop's flesh.
The smell of the feast drifts through the water
and attracts scavengers.
Whelks.
They are the clean-up crew.
Tidal beds like these can easily be destroyed by bottom-trawling.
Protecting those that survive is essential
if we are to preserve the richness of our seas.
100 miles from mainland Scotland lies Shetland,
the most northerly part of the British Isles.
Because this archipelago is in the open ocean,
it has some of our cleanest waters.
This is one of the reasons why Shetland
is our main stronghold for otters.
More than 1,000 live along its 1,600 miles of undisturbed coastline.
Shetland's isolation and its relative lack of pollution
suits these animals very well.
Elsewhere, most live in or beside rivers,
but here they spend much of their time in the sea.
Each has its own territory
and knows where its prey is likely to be hiding.
But the waters in which they spend so much of their time are chilly,
and otters need a lot of food to keep themselves warm.
They can hold their breath for up to 90 seconds...
...and reach hunting grounds as deep as ten metres.
In summer, the waters teem with small fish, such as eelpout,
which are easy to catch and are excellent food for the cubs.
Little wonder that Shetland has the greatest density of otters
anywhere in Europe.
Otters are not the only stars in Shetland's natural history.
Around its coast are habitats of global importance.
Forests of kelp.
They are among the thickest and most vigorous of their kind
in Britain and Ireland,
with individuals growing to over two metres tall.
Like the seagrass, this underwater forest
captures great quantities of carbon...
...and provides a home for a wide range of animals.
One type of kelp here, the furbellow,
has an especially feisty resident.
Its hollow base is the favourite home of clingfish.
This minute two-centimetre-long male
has been left by his female to look after the eggs.
Hundreds of them are glued to the interior of a furbellow's stem...
...and they're almost ready to hatch.
It's quite a responsibility for him.
All day long, he fans fresh, oxygen-rich sea water
across the eggs.
He inspects them regularly
and quickly removes any that are infertile or dead.
But his nursery is under attack.
Sea urchins are devouring the furbellow.
Their powerful jaws are destroying the clingfish's home.
His babies are under threat, still stuck to the walls of their nursery.
There is no escape.
Their tiny father takes action.
He tries to drive the urchins away by beating his tail.
But it makes little difference.
Time for another strategy.
The urchins are covered in sharp spines...
...so the brave little father nips the urchins' sensitive tubed feet.
Finally, the urchins give up and go in search of easier meals.
The little male clingfish has saved his young.
He is part of a crucial community
that maintains the balance in this marine rainforest.
At the height of summer, the power of the sun combines
with the stirring action of the tides and the waves...
...and the ocean blooms.
The creators of these blooms
are myriads of floating, microscopic algae.
They are the basis of the entire food chain in the open ocean.
And when conditions are right, they multiply at an astonishing rate.
Their repeated blooms are one of the main reasons
why the seas around Britain and Ireland are so productive.
The floating plants support a great community of tiny floating animals,
the zooplankton.
Tiny creatures that drift in great clouds driven by the ocean currents.
Among them are copepods, tiny crustaceans
that feed on the microscopic algae floating alongside them.
The rest are mainly predators.
Many of these are also tiny.
The larvae of bottom-living animals like lobsters and crabs,
some only 5mm long.
There are also sea gooseberries,
which propel themselves through the water
with rows of pulsating bristles.
They may look fragile, but they are surprisingly effective hunters.
They extend long, thread-like tentacles.
Other drifters that get entangled are reeled-in and eaten.
The sea gooseberries themselves, of course,
are also prey for larger predators...
...such as the melon comb jelly.
It has a particularly large mouth.
When it opens it, the suction it creates
pulls its prey straight into its stomach.
Despite the richness of our seas,
climate change is seriously reducing the amount of zooplankton.
And this has an effect on the entire marine food chain,
right up to real giants.
The largest fish in our waters is as long as a double-decker bus.
The basking shark.
It uses special sieve-like structures on its gills
to filter out the zooplankton.
And they feed on nothing else.
In summer, these giants come close to the coast all around our isles.
They're normally solitary,
but when the plankton reaches the peak of its abundance,
the sharks come together.
They swim in formation.
Plankton that escapes one mouth will be scooped-up by the next.
In just a few special places
along the western coasts of Britain and Ireland,
basking sharks gather in large numbers to feed and breed.
Thousands find their way here each year...
...a major part of the global population.
Plankton feeders come in all sizes.
Sand eels are only 30 centimetres long,
but they occur in vast shoals.
Like so many species, overfishing and warming seas
have drastically reduced their numbers.
They are essential prey for a wide range of top predators.
Dolphins scour vast areas of the open ocean to track down the shoals.
And following the dolphins comes an ocean legend...
...bluefin tuna.
Weighing up to 700 kilos
and with a top speed of more than 40mph,
these powerful predators can make quick work of the shoal.
Bluefins have been absent from our waters for more than 50 years.
And they have only recently returned.
If they are to stay,
the overfishing of our seas will have to be stopped.
In the sky above...
...gannets, looking for fish such as mackerel and herring.
They hit the water at over 60mph.
The impact is enormous.
To avoid breaking their wings, they fold them back
and turn themselves into streamlined arrows.
65% of the world's population of northern gannets
find their food in our seas.
But perhaps the bird that depends most on the still-rich waters
around Britain and Ireland is the Manx shearwater.
Every year, our coasts are visited
by almost the entire global population of this sea bird.
Here in Cardigan Bay off central Wales,
they gather in their thousands,
attracted by the richness of our seas.
Each summer, 350,000 pairs all return
to this tiny island of Skomer off the Pembrokeshire coast.
This is the largest breeding colony in the world
and most of the island is honeycombed with their burrows.
Tonight, under the cover of darkness,
their chicks are starting to leave these burrows
for the very first time.
Watching them do so is an unforgettable privilege.
This young bird has just emerged from its nest hole,
maybe for the first time.
It's about to make the most important journey of its life.
And it needs to get every inch of altitude before it takes off.
I can just see beyond me...
...there are more of them.
One, two, three, four.
It's just exercising its wings...
...in preparation for this extraordinary flight...
...which will take it 6,000 miles across the oceans
to South America, to Brazil and Argentina.
And then, after some four years,
once again it will set out on a long oceanic journey,
a further 6,000 miles back to this one small island of Skomer.
Are you going to go?
It's hesitating and who can blame it?
An enormous journey awaits it once it takes off from here.
This is the headquarters of this astonishing species
...and we are its custodians.
Come along. Come along.
Are you about to take off?
Good luck!
What an astonishment.
A lot has changed in my lifetime
and today the wildlife we still have
faces greater threats than ever before.
Our sea birds remind us that here in Britain and Ireland
we are very fortunate to have some of nature's greatest spectacles
right on our doorstep.
Because this is our home,
it can only be our responsibility to restore and protect our wildlife.
Perhaps you can be the first to pass these wild isles
on to the next generation in better shape than you inherited them.
From the Isles of Scilly in the south, to Shetland in the north,
the ocean team spent 300 days filming the marine wildlife
of the British Isles as never before.
They captured new behaviours,
experienced the worst of the Atlantic weather,
and witnessed intimate moments in the lives of our ocean wildlife.
Doug Anderson, is one of the world's leading underwater camera operators.
He's worked all over the planet,
filming some of the ocean's greatest spectacles and largest inhabitants.
And for this series, he filmed the majority of the ocean episode.
His passion for the underwater world began on the Isle of Arran,
off the west coast of Scotland.
My first underwater experience was in Lamlash Bay
in front of my grandparents' house
and it is burnt into my memory.
My dad had made me a wet suit and I remember putting my face underwater
and just being blown away but the wildness of it.
You know, there were crabs and little fish
and it felt like a wild place.
I remember lifting my head up
and looking over my shoulder back at the village -
there was, like, the policeman doing his round,
and people going to the shop and I was like,
"Oh, the ocean is a wild place and behind me is what people do."
And I never recovered.
After learning to dive,
Doug's passion for the underwater world
took him on a journey far from home.
I eventually got a job on a series called The Blue Planet,
back in the mid-'90s.
And then just found myself on plane out to the Azores.
Yeah, I was, like, 27 years old, and that was the start.
Until now, he's never had the chance to show
what the British Isles has to offer.
On the Wild Isles project, it just felt like an amazing opportunity
and responsibility to take everything I've learned
in 25 years of working all over the planet,
and just applying all of that to here.
Although they might be easier to reach,
our waters have their own challenges.
This project, in many ways,
has been the hardest professional experience of my life.
Everything that you do on the ocean in the North Atlantic is tough.
We can have four seasons in a day.
This unpredictability makes filming in our seas
a matter of boom or bust.
The team must be on constant standby
to mobilise quickly when conditions are right.
In Shetland, they're heading for the seabed.
To record life down here,
Doug has designed and built his own bespoke underwater tripod.
High-powered lights illuminate the seafloor...
...and weights stabilise the rig,
allowing Doug to film a time-lapse of these slow-moving creatures,
revealing a world that few people will ever see in actuality.
Below the kelp, Doug takes his design a step further -
a motion-controlled slider for tracking timelapses.
Now, he can move the camera with pinpoint accuracy,
revealing how urchins travel through this marine forest.
A shot that's taken months of preparation.
But not everything in our oceans is as slow-moving.
Off the coast of Cornwall,
the team are chasing one of the ocean's fastest inhabitants,
bluefin tuna.
They have only retuned to our waters in the last few years.
We've got all the ingredients that we need here.
We've got dolphins, we've got tuna,
there's gannets here, and shearwaters.
But we need it to come together into something that we can film,
and that's a bait ball.
So it has to be a patch of fish jammed up against the surface
in reasonable visibility to make it work, so...
...fingers crossed.
Bait balls don't last long.
They can be over in a matter of minutes.
So to film tuna hunting, speed is everything.
Radio call from one of our contacts, so we screamed down there,
only to discover we were just a few moments too late.
Which is really frustrating. We've got a really fast boat.
This is so new, this set-up here, these bait fish coming here.
It's five years, so we're just...
Everyone's just working it out and it seems like we're not alone
cos it's like the dolphin and the tuna are just beginning to find it
and exploit the resource as well.
The team use a drone to help locate the tuna
before the bait balls disappear.
The exciting thing is, this is England.
We've got literally Falmouth right there
and we've got these crazy pods of common dolphins rolling through
and there's bluefin showing every now and then.
It's an amazing kind of ocean scene.
Although it looks good from the air,
poor visibility underwater prevents Doug from getting a clear shot.
Yeah, a total glimpse, just like the briefest of moment.
Pretty green water, I just get in,
and they just come through and just roll through.
In the hope of finding clearer water, the team change location.
We're further down the coast.
We're going to be working further offshore,
and we're going to be trying to join the blue water with the bluefin.
If a big patch of pilchards on the surface or mackerel comes together,
then come away with what we want from this.
We have tuna, they're all over the place just now.
We just need to wait for this sort of pot to boil, you know.
For the bait to come together into a lump
for long enough, for it to go static so that we can get in and film it.
The plan works!
The team finally get the conditions they have been seeking for so long.
To actually see a bluefin tuna underwater in England
is just unbelievable.
The return of bluefin tuna to our waters
is a sign that their population is recovering.
But it's still a fraction of what their numbers could be.
Since Doug left Arran over two decades ago,
the coastal community, including his family,
created Scotland's first marine No Take Zone.
Since its creation in Lamlash Bay, biodiversity has increased fourfold.
But it's one of just a handful of No Take Zones around our wild isles,
that combined, cover less than 1% of our sea.
The abundance of life within them
spills out into the surrounding waters,
enriching and strengthening the wider marine environment
The way to get British seas back is to allow large areas
to return to a natural state,
and maintain those very highly protected areas for a long time.
For Doug, celebrating the beauty of British waters
has been a chance for him to give something back.
If I can play a tiny part about providing the visuals
to allow that conversation to happen in a meaningful way,
for people on all sides of the argument
to imagine what lies beneath those grey waves,
then I think it would be an extraordinary thing.
The Open University has produced a free poster
exploring our Wild Isles and their diverse habitat and species.
Order your copy by calling...
...or go to...
...and follow the links
to the Open University.
If you'd like to play your part in restoring our Wild Isles
and learn more about what you can do to help,
just search Wild Isles on the BBC website.