The Bustling South Britain's Secret Seas

The waters around the UK

hide treasures and surprises we rarely get to see.

Powered by Arctic currents to the north

and the Gulf Stream from the south,

our island occupies a unique position

in the Atlantic ocean.

'I'm explorer Paul Rose.

'I was Base Commander of the British Antarctic survey for ten years

'and I've scuba-dived all around the world.'

I've got to be careful doing this! Oop!

But now I've come home

to lead a team of specialists

to uncover the secrets beneath our seas.

Divers up!

Joining me is marine biologist Tooni Mahto.

Her underwater expertise

will reveal the unexpected riches

of British marine life.

This is a colony of loads of individual animals.

Journalist and underwater archaeologist Frank Pope

will examine the bigger picture of our relationship with the sea

and explore our maritime history.

The remains of the 60-odd crew men are still inside.

This series will take us on a journey right around the British coastline,

to uncover the most startling underwater wonders.

This time, we're exploring Britain's south coast.

It's our busiest coastline,

packed with ferries,

fun-seekers and pleasure boats.

But below it all,

there are mysterious wrecks and magical creatures.

This time we're investigating our bustling southern shores.

Beneath our waves is a world of secrets.

Our expedition begins in Poole,

bang in the middle of Britain's south coast.

This busy seaport

has been a hub of maritime activity

since the 12th century.

But just metres below the waves lies a secret,

which has lain untouched for centuries.

Out there in the Swash Channel, archaeologists have uncovered a mysterious wooden shipwreck.

It's a spectacular wreck, we know that much, but not much more.

-It's full of secrets and mystery.

-Look at that!

-Have you ever seen anything like that?

-Certainly not.

That's a very intricate carving.

No-one knows when it sailed, no-one knows exactly who built it,

where it was going, or even how it sank.

-There's no records of this thing at all.

-I'm really looking forward to this.

I've used all kinds of tools underwater,

but not on something as delicate and as precise and as important

as maritime archaeology.

So I'm super-keen on this one.

-You will be careful won't you, Paul?

-Yes, I'll do me best!

Frank and I are joining a team of archaeologists from Bournemouth University

who have been working on the site night and day.

We want to find out all we can about this puzzling wreck.

'I didn't realise how close we would be to passing ships.'

Here comes the Cherbourg ferry

in the main shipping lane called the Swash Channel.

It's defined by... You can see these buoys -

there's the green one there and the red one right there.

And our wreck, the Swash Channel wreck,

is right underneath us, on the very edge of the channel.

The wreck would have laid there undiscovered,

seven metres below the surface,

were it not for a dredging boat

clearing a channel for the ferries.

'Head archaeologist Dave Parham

'has drawn a sketch map of the site.'

And this was actually part of the bow castle.

We've also got the gudgeons for the rudder.

-But the rudder is in front of...

-The rudder has come off,

it's become displaced and swept underneath the wreck and then covered in sediment.

-If it hadn't been covered in sediment it wouldn't have survived.

-So lucky!

-Unusual to find a rudder.

'The archaeologists believe the wreck dates from the 17th century.

'With no historical records,

'her true identity remains unknown.'

As an archaeologist, your job is to try and put together the different clues

that might give you a picture of what the wreck was

and the sort of people that lived in her.

The thing is, when you first get down to it,

it's going to be enormously confusing,

its going to be a very distorted picture, and often incomplete.

What you're going to do, boys,

is go down to this part of the wreck here.

What we want you to do is dig along here to try and define this edge.

Be aware there are fairly delicate things lying around.

If you're going to sit down, look at what you're sitting on first.

LAUGHTER

Are we ready to go?

Have a good one.

'Lying at only seven metres,

'it takes just moments to reach the wreck.'

Oh, look at this!

Oh, wow.

Look at that!

Now, this is interesting.

-These large pieces of wood look like ribs of some kind, don't they?

-Yep.

It's beautiful condition, you see here where the wood has been freshly exposed.

It's absolutely beautiful, it's mint condition.

That's fabulous.

'As an archaeologist himself,

'Frank starts to recognise parts of the ship we're swimming over.'

You can see the big frames of the ship.

Gosh, she was really quite a heavy ship.

And these amorphous lumps...

These are actually the heads of iron bolts

that would have helped held the ship together.

They've kind of erupted in this reaction with the seawater.

'While Frank looks for more clues,

'I join one of the team excavating new parts of the wreck.'

This here's the dredge

and it's like an industrial underwater vacuum cleaner.

You know, I've used these water dredges

as part of salvage work before,

but I must say I've never used them to try and reveal an ancient ship.

You can see I can quite carefully expose these ancient timbers,

just a centimetre at a time.

The sediment, sucked up here,

gets pumped out again fifteen metres away,

so it doesn't settle back over the wreck.

Blimey, I nearly sucked a fish up then! Look at that.

He must be a strong swimmer.

'Every tree has a unique pattern of growth rings,

'which can be matched against a global database to identify it.

'By analysing the timbers,

'the archaeologists have discovered

'that the ship was built from wood felled in 1629.

'They can even tell that this wood

'came from close to the border between Germany and Holland.'

When you see what I'm doing here

and then look at the amount of wood that's been exposed,

you get a pretty good idea of how hard work it is. This is a big job.

'From her size and design,

'the archaeologists know this was a merchant vessel,

'and the discovery of a layer of pine over the hull

'gives them a clue as to where she was headed.'

This is beautiful. So what you can really see here is the two types of wood.

This is the actual hull of the ship here.

This is the hard wood and then the sacrificial layer on top which is made of pine.

'This protective cladding

'was only found on ships heading for the warm waters of the tropics.'

It's fascinating to see.

I've never seen this on a site before

and you can only see it on a couple of other sites around the world.

'This ship was part of the very beginnings of trade with the East,

'but it was carrying more than just cargo.'

Oh, holy smokes!

I've just figured out what this is.

This is a cannon.

I could have just swum over this and think it was a white rock.

'This is just one of six cannon the team have discovered,

'making her a heavily-armed merchant ship.'

This is a big old gun,

probably a 24-pounder.

'The excavation work has revealed much about this important ship,

'but Dave Parham has taken Frank to see one discovery

'which marks this wreck as something quite extraordinary -

'the ship's rudder.'

Up here, we have the carving of a human head.

Wow! Look at that.

You've got the hair, his face,

an eye socket with an eye in it,

his nose and a moustache on his mouth.

I have never seen anything like it.

It's absolutely beautiful.

Wow, what a thing!

This is like finding a pharaoh's tomb.

'This intricate carving is one of three they've found so far.

'It covers just the top part of the rudder,

'which is over eight-metres long and weighs almost two tonnes.'

This isn't just any old wreck, this was a really high-profile ship

and you can tell that by the carving.

'Piecing together the clues,

'we can now start to build a picture

'of what this ship may have looked like.

'This was a large wooden trading ship,

'built at a time when Charles I was on our throne

'and Europe was engaged in the very beginnings of empire building.

'From the timber,

'we know she sailed from Holland or Germany

'and was headed to the tropics.

'But the heavy cannon and ornate carvings

'suggest this was far more than just a standard merchant ship.

A beautiful wreck, my God.

You know what's so poignant is

you've got this wonderfully-carved wood that's just been exposed

and you can almost see the chisel marks of the guys who made this. This was hundreds of years ago -

probably 1630 that this stuff was made -

and it's right there. And by touching it, you really feel

like you're connecting with the guys who built that and who sailed in it.

'After months of excavation,

'the fate of this important wreck

'now hangs in the balance.

'Saving a ship like this

'is a complex and expensive process.

'But the archaeologists are running out of time,

'as the wreck is being destroyed before their eyes.

'Later on, we'll be back to find out why.'

The English Channel is the world's busiest shipping lane,

so it's no surprise that our southern waters are full of wrecks.

But the shipwrecks of the Channel don't just give us a glimpse back in time...

they're also home to some surprising sea creatures.

There's one animal which is renowned for hiding out in wrecks.

Rumoured to be big, vicious,

and no friend to divers.

The beast in question is the conger eel

and despite being one of the most common animals in our waters,

it's also one of the most secretive.

We really don't know much about them.

I want to find out if this giant beast

really does deserve its fearsome reputation.

'Here in Plymouth,

'I've found some conger experts.

'But they're not biologists, they're expert anglers.'

So what is it about the conger eel

that evokes such a passion for it?

I'll tell you what it is.

It's mean, moody

and magnificent.

And I think that sums up the conger eel.

'Bryn Lavis and Mike Millman

'run the British Conger Club

'and are devoted to all things conger.'

Now then, what's the biggest one that's ever been caught in British waters?

133-and-a-quarter pounds, by Vic Evans out of Brixham.

I mean, it's a mighty eel.

-Boy, that is a whopper.

-Yeah.

133 pounds and the width of this one?

It's about 42 inches at its widest point.

42 inches - hang on... Bigger than my chest, and how long?

Nine feet...plus.

-Nine feet, two inches, I think it was.

-Holy smokes!

So when you catch them

and all of a sudden you've got this huge great thing on board,

what happens then?

-Well, it's not finished.

-No, I can imagine!

Cos there must be teeth going and there's a lot of activity.

It's not so much the teeth that are the problem,

they've got very small teeth.

But they've got a terrific clamp pressure.

Think of a crocodile, an alligator.

If they've got hold of something and try to get away,

-they start revolving...

-So here's your finger?

-Oh gone, just twisted off.

-It is ripping off?

Yes, it's rip. It's not a bite off, it's rip off.

Ow!

'The Conger Club are sport fishermen

'and they throw the congers back in once they've landed them,

'but I don't want to catch one.

'I want to dive into conger territory

'to see just how close I can get

'to one of these ferocious beasts.

'Although congers are found all along our southwest coast,

'the deep waters of Plymouth Harbour are famous for congers.

'Massive eels have been caught just metres from these shores.'

Conger eels are really opportunistic hunters - they'll eat anything, even each other!

I'm going to take some mackerel with me to entice them out of their lair.

And I'm going to take no chances whatsoever,

so I've got these special Kevlar gloves just in case.

Away you go, Paul.

'Can you hear me?'

Yeah, I can hear you loud and clear.

Have a good dive, fellas.

Good luck with the congers.

'30 metres down is a wreck,

'one of almost 5,000 in the English Channel.

'It should be the perfect conger hideout.'

There's a fair bit of nice life down here.

That's a good sign, look at that.

'It won't be easy to get close to a conger.

'They're ambush predators

'and tend to hide away in nooks and crannies

'so they can lash out at passing prey.

'That's not the kind of close encounter I'm after!'

It stands to reason we should find them in some of these holes.

Oh, there she is!

Look at this.

Now, with any luck,

with some of this squid bait,

I just might get her out.

I've got to be careful doing this

because she's got very sharp teeth.

Come on then, girl, out you come.

Ooh!

Ha!

You notice I'm saying "her" and not "it" or "him",

and that's because I'm absolutely certain that she is a female.

Cos we never see males in our waters. Never, not one.

'Female congers spend up to 15 years in our waters

'before heading to deep Atlantic seas to breed.

'Scientists think they may be drawn to our rich waters

'so they can fatten up before spawning.

'But they've still no idea where the males go.'

Here she comes.

Here she comes.

'She seems pretty fearless.

'I'm amazed how close she's letting me get to her.'

Ooh!

Ha-ha!

I don't think we're going to get this one out, you know.

She's too smart for me,

no surprise there.

See you.

'That conger was less than a metre long,

'certainly not one of the giants the anglers were talking about.

'So I'm going to keep on looking.'

These are the boilers.

And you can imagine all these great holes are perfect places for conger.

I've found one!

She's just a beauty!

She is a beauty.

Look at her!

I don't even have to feed this one,

she's just curious as to what's going on.

I know the anglers said they were mean, moody and magnificent,

At the moment, I'm just going to stick with the last one -

magnificent. She is beautiful.

Hello! How are you?

HE LAUGHS

Hello!

Well, this is a tremendous experience.

I'm not going to stick my fingers in there so she can get it,

that's for sure.

'She's certainly not the fearsome monster I was led to expect.

'In its own environment,

'the beautiful conger eel is a secretive and magnificent creature.'

'And in all my years of diving,

'I can honestly say I've never been kissed by a fish before!'

I think that was the perfect conger eel encounter.

I don't think you could possibly get any better.

You could get a sense of the beauty and grace of this fabulous animal,

even though she was one side of the boiler and I was on the other.

I'm in love!

The calm seas and warm climate of the south

bring a huge variety of marine animals to these shores.

But they're not the only ones who flock here.

The wildlife has to share these seas.

In Dorset's Studland Bay, there's a conflict of interest

between our actions and the needs of some very special marine creatures.

Tooni went to investigate.

This bay is home to one of Britain's most unexpected inhabitants.

Small in size, but large in character,

you might think you'd only see them in tropical waters.

But Studland Bay is famous for its seahorses.

Six years ago, local conservationist Steve Trewhella

discovered a pregnant seahorse here,

suggesting that Studland Bay is home to a breeding colony.

I know it sounds silly, but when we're looking for seahorses

you have to go into seahorse mode.

You have to think like a seahorse. Where would you be if you were a seahorse?

They are very, very hard to find.

Studland Bay is now recognised as one of the most important seahorse sites in Europe,

and there's a good reason they're here.

'Just a few metres deep, lies this bed of thick eel grass,

'a perfect seahorse habitat,

'but one that makes them difficult to find.'

So, Steve, what's the best method to try to find seahorses in the eel grass?

A combination of extreme patience and good eyesight!

You have to just really take your time

-and just sort of sweep through carefully.

-OK.

Eel grass needs shallow, protected waters to flourish,

so the sheltered bays of the south coast are ideal.

Eel grass beds are incredibly important for a whole range of species,

because it provides this fantastic wealth of places to hide,

it would be incredibly difficult

for a predator to come in here and find anything,

as it's proving for us to find a seahorse.

Ha-ha!

Look! I have found a spiny seahorse.

I know you're not meant to get sentimental about creatures,

but she's so beautiful.

Astonishing!

'Seahorses may not look like it,

'but they are in fact fish.

'They blend into the weeds,

'and prey upon passing tiny animals.'

And these little spines that are coming off her head,

they help her camouflage herself

to basically disappear into the eel grass.

'We've only just discovered that seahorses are breeding here,

'and yet we could be about to lose them.

'The rich eel grass essential for their survival is incredibly fragile

'and is being destroyed...by us.'

'While I'm with the seahorses,

'Frank is finding out how this precious habitat is being damaged.'

These mooring buoys look pretty harmless,

but underneath this float and the rope

there's about a ten-metre length of chain sitting on the sea bed.

And every time the tide changes,

that chain scythes round in a circle and before long,

you've got a 20-metre wide bald patch on the sea bed.

These chains are the big problem.

Just adjacent to it, it's just bare sand

and I literally can't see any eel grass growing around me.

I mean, it's cleared as far as I can see.

And it's not just the buoys.

At the height of the summer,

there are up to 300 boats dropping anchor in this bay.

It's difficult to persuade people that doing something like chucking an anchor into what looks like weeds,

is actually destroying a very vulnerable and critical habitat.

'To study the impact on the seahorse population,

'Steve has been closely monitoring them.

'He has a special licence to tag these tiny creatures

'and track their movements.'

Bearing in mind they're not radio tags, they're purely visual -

you have re-find the animal -

it proves that they're highly territorial.

We're going back to the same location every week

and re-finding many of these tagged seahorses.

Well, I sincerely hope that you see her again later in the year

and that you manage to see her a few times.

Well, hopefully we will,

and next time we see her she may well be with a mate,

so, hopefully breeding successfully - that's what she's come here to do.

Bye-bye, beautiful.

When you look out on Studland Bay,

it's easy to see how the destruction of this precious seahorse habitat

is going unnoticed.

By highlighting the plight of the seahorses

and the importance of the eel grass they live in,

perhaps the conservationists can now raise public awareness

and keep these magical creatures safe.

'Just north of Studland Bay, Frank and I are back with the team

'investigating the Swash Channel wreck,

'one of the archaeological finds of the century.

'But time is running out...'

The archaeologists are working every hour they can

to document and excavate the mysterious Swash Channel wreck.

Frank is underwater with them now

to investigate why the archaeologists have to work so fast

in order to save this wreck.

All of what you see here is only here

because it was once covered by sediment.

That sediment's now gone.

'The natural erosion of the sea bed,

'which has exposed the wreck from beneath the sand

'has also exposed her to danger.'

First of all, you get the scouring from the sand as the currents swish past

and then you also expose it to oxygen

and therefore bacterial decay starts eating the wood.

But there is one further, much more sinister threat

that this wreck faces.

'She's now under attack from some small but brutal sea creatures.'

At Bournemouth University, marine archaeologist Paola Palma

is trying to find out how fast the ship is being destroyed.

The surface of the wreck is being eaten away

by a small crustacean called a gribble.

-Hi.

-Hi.

'Tooni's gone to her lab

'to see these shipwreck wreckers for herself.'

So these are obviously very tiny

and they don't go inside the core of the wood,

but they stay on the surface.

And what they do, they cause all this superficial degradation.

-Bits flaking...

-Yes, bits falling off everywhere.

-Absolutely.

The damage that these organisms cause is fast

and is quite ferocious.

But as damaging as the gribble is,

there's an even more destructive animal at large on the wreck.

So the gribbles are causing this roughing of the surface,

but it's something different that's causing this actual real structural damage.

It is indeed. This is the shipworm.

And you can see it even better here.

You see a perfect example

of the kind of tunnels that are left by the shipworm.

You can also smell it, probably!

-I can!

-It smells quite badly, doesn't it?

And it's something that...

looks like this...

It turns out shipworm is not a worm at all, but a mollusc,

like a mussel or a cockle.

They burrow into the wood,

leaving behind them these chalk-lined tunnels.

But to see the full extent of the damage,

we need to take a look inside.

A bit of archaeological baking.

Back in a minute.

As you can see, they are quite impressive.

You can even see, very clearly,

the shell of the organism.

I guess the main thing about the shipworm is that it's not actually biting into the wood,

it's literally boring into the wood with these incredibly impressive bivalve shells.

And it's only when you see them on the close-up on the microscope,

that you see every single serrated edge.

And it's actually this rotation of this shell

that's literally diving and digging down

into the timbers of the shipwreck.

Parts of this wreck could be entirely destroyed by these creatures

in just a few short years.

It's an absolute disaster.

We're not just talking about one single organism,

but we're talking about millions of organisms.

So the damage that they cause is absolutely, you know, horrendous.

We're seeing that already, in one year,

the damage is irreversible.

'Back on the Swash Channel wreck,

'lead archaeologist Dave Parham

'is all too aware of the damage these creatures cause.'

This is what the timber surface would've been like when it was first uncovered.

Outside of that you can see shipworm and gribble tunnels.

This is really a case study in how well sediment can preserve wood.

Cos when this is covered, this is protected.

But give it a few years and it'll be gone completely.

And that same degradation you can see all the way along the line.

This wood is rotting away before our eyes.

So there's a real sense of urgency here.

With the site under attack and the clock ticking,

Dave and his team must do everything they can

to preserve this precious ship.

Frank and I will be looking into this later.

Our southern shores host some of Britain's favourite holiday destinations,

with seaside attractions and beaches drawing millions of people.

But sometimes the real treasures are just beneath our feet.

Tooni's gone to Brighton to see what's beside us,

when we're beside the sea.

Brighton, in East Sussex,

was one of the UK's first seaside resorts

and still throngs with visitors today,

attracting over eight million people a year.

And many of them will visit Brighton's famous palace pier.

It was built in 1899,

at a time when the well-to-do liked to stride out into the ocean,

gaze across the sea, decide which small nation to conquer next,

all without getting their feet wet.

But I'm not here for the fairground rides and candy floss,

I've come to see the attractions below the pier.

It may have been built for pleasure,

but this pier has created a huge artificial reef.

And we've been given special permission to go underneath it.

This 500-metre long intricate lattice of steel beams

creates the habitat that allows marine life to flourish.

That looks good. Does it feel OK?

-MUFFLED

-That feels good.

It's very eerie being down here underneath the pier.

Funny to think of everybody playing the slot machines and eating doughnuts above.

'The first arrivals to colonise this space

'would have been the "clingers"

'- barnacles and mussels.

'Without rocks to latch on to,

'these creatures would not be here.

'But the steel beams of the pier

'effectively create a 12-metre skyscraper for them to live on.'

This is just absolutely jam-packed full of mussels,

all filter feeding and open.

And where one thing comes, many others will too

and you get an entire eco-system,

so predator and prey.

But it's the mussels and the starfish

that are right at the basis of that food chain here.

These starfish are the mussels' worst enemy.

They're actually voracious predators,

but they feed on mussels in quite an interesting way.

The starfish yank the shell apart

and then evert their stomachs.

So they literally pull their stomach out through their mouth,

sink it into the mussel

and digest the mussel in its own shell.

Everywhere you look, it's just mussel, after mussel, after mussel,

being eaten by starfish, after starfish, after starfish.

'And mussels aren't their only prey.

'This whelk will soon succumb to the starfish's deadly embrace.'

Look at this amazing fish.

It's a gurnard.

They live completely on the sea floor, don't really swim that much.

Camouflage is their main defence against predators.

What we're swimming over at the moment

is pretty much what the sea floor would have been like

had the Victorians not built this pier above.

Flat, barren with not much for life to cling on to.

Here, on the other hand,

marine life has completely encrusted the surfaces of these metal structures.

SHE LAUGHS

Little tompot blenny

just hiding in this pipe here.

They're really beautiful fish.

Just goes to show that every single nook and cranny

is utilised by one animal or another.

'It may have started as a Victorian playground,

'but this pier is now a thriving eco-system,

'home to millions of sea creatures.'

-SHE LAUGHS

-Now you see him, now you don't!

It's remarkable.

'It's good to know that sometimes our actions help marine life to prosper...

'even if it's entirely accidental.'

Good down there?

Yep, it's very, very murky.

It's crazy and gloomy down there.

And it's hilarious just coming out

and watching people walking along on the pier above you

and hearing this thumping music,

when you've just been down amongst the peace and quiet

and the gloom of the mussel beds.

Fantastic.

Nearly 200 kilometres away from the bustle of Brighton is Lyme Bay,

part of Dorset's sweeping Jurassic coast.

This huge sheltered cove, warmed by the gulf stream,

is one of the country's richest areas of marine life

and home to beautiful British corals.

But it's also an area vital to our fishing industry.

Scallops are one of my favourite foods

and the ones here in Lyme Bay are just legendary.

But while we might all enjoy a tasty fish supper,

how much do we really know about the journey our seafood takes

from the sea floor to our dinner plate?

Increasing numbers of us choose to buy free-range chickens

or organic beef.

But how many of us ask how our seafood is sourced?

Most scallops are caught by dredging.

Dredgers are great heavy metal rakes that get dragged along the sea bed,

a bit like my fingers in the sand.

And they're very, very efficient,

collecting thousands upon thousands of scallops.

But the problem is they collect everything on the sea floor,

not just the scallops.

'To see first-hand the impact dredging may have on our seabed,

'Tooni has gone out into Lyme Bay.'

There's a lot of debate about the pros and cons of dredging.

Is our love of seafood putting the marine environment at risk,

or can we find a way for the two to peacefully co-exist?

'I'm going in,

'to explore the scallop beds which get regularly dredged.'

'The only scallops left here are the ones too small for the dredge nets.'

SHE GIGGLES

Such funny animals!

They are total comedy molluscs.

Love them.

It's as though they're puppets being pulled by strings.

Off you go.

SHE LAUGHS

That movement is actually the adductor muscle inside them

which opens and shuts the shell.

But unfortunately, it's that that we're so keen on eating.

'Although the dredgers are designed

'to leave the smaller scallops behind,

'as they trawl a path across the sea bed

'there's little else left in their wake.'

Eugh. Such a muddy, horrible bit of seabed.

It just feels really desolate,

like a desert, essentially.

I don't know. It really does feel like some huge destructive force

has really gone through the whole place

and just left it a real wasteland.

'But left alone,

'the sea bed can look very different.

'I've come to another part of the bay

'where the sea floor is scattered with large boulders.

'These can damage the towing gear,

'so this area has never been dredged.'

'This reef is home to some extraordinary creatures.

'These pink sea fans are actually slow-growing, cold-water corals.'

This is a colony of loads of individual animals,

growing in this wonderful fan-shaped structure.

Now, they're all aligned, perpendicular to the current,

which flows directly through them.

That's so they get the maximum amount of food.

Now the thing about pink sea fans is

they're exceptionally slow-growing.

This colony here would be about 10 to 15 years old.

What a beautiful perch of reef.

Not something you'd expect off the south coast of Britain.

To protect this fragile marine environment,

the government has now made part of Lyme Bay an exclusion zone.

Within these 155 square kilometres,

no scallop dredging is allowed.

But not everyone is a fan of the protection scheme.

The fishermen here feel that the exclusion zone is too big

and that they are paying the price.

Nick Prust has been fishing this area since he was 15.

A lot of our most lucrative grounds are now taken.

What we're saying is, within the Lyme Bay closure area,

there are areas that are not reef,

that hold considerable stocks of scallops

-that could still be fished.

-Right.

The worrying part is the speed that it's all happening.

To us, it's too much, too quick.

What do you think are the solutions for Lyme Bay?

Areas should be opened up, away from the reefs,

we know where they are,

and let the fishing industry continue to fish,

because it'll work.

This is a complex issue

and tensions are understandably high.

Is there a way to protect the livelihoods of our fishermen,

without destroying our slow-growing corals?

We're a nation of fish-eaters

and it's our demand that drives the dredging industry,

so it doesn't help to point the finger at fishermen

whose livelihood depends on that dredging.

There are no easy answers, but ultimately we all have a choice.

So the next time you buy fish,

it's worth asking where it comes from and how it's been caught.

'Delicate corals aren't the only secrets hidden in Lyme Bay.'

Its strategic position and calm waters

led to it becoming the site of a key naval base

which played a crucial role in both world wars.

'Frank is delving into the fascinating story

'of a truly incredible naval invention.'

She was a British submarine called the M2

and she's got a unique place in Royal Naval history.

The HMS M2 was built in 1920

and was originally fitted with a single 12-inch gun.

But after four years,

she was withdrawn from service

and reassigned for experimental use.

The navy had a cunning idea.

They took the huge gun off the M2

and replaced it with a watertight aircraft hangar.

Then they commissioned a miniature two-seat biplane

that fitted inside it,

and could be catapulted off the front.

Suddenly, the navy had an incredible new weapon.

They had the range and stealth of a submarine,

but they also had an eye in the sky.

The ingenious plan was to send her ahead of the battle fleet

as a reconnaissance scout.

The sub would surface,

its tiny plane unfolded and launched,

all within a matter of minutes.

'As a marine archaeologist,

'I've always been fascinated by the history of the M2

'and the dive support team are keen to hear her story.'

That's obviously them launching the plane out the hangar,

but look at how low in the water she is.

-That looks hairy to me.

-No freeboard there at all.

The pilot would sit there with the engine going...

HE IMITATES ENGINE

..screaming, and then go...

and give the thumbs up,

and then on the deck beside him is the stoker.

The stoker is the guy that can launch the catapult,

but he can't actually do it himself,

because you have to wait for the captain's word.

So he signals up to the seaman on the conning tower,

who turns to the captain and goes, "Ready to launch, Sir?"

Meanwhile the guy is still... And then the captain goes, "Launch",

and the seaman goes "OK, launch" and goes like this to the stoker

who finally goes "Boof", and releases the catapult

and they hit 60 knots in - how far is that? About 40 foot.

It was an ambitious design.

But perhaps it's no surprise

that this eccentric vessel wasn't without its problems.

On the 26th January 1932 during routine exercises,

the M2 disappeared.

Eight days later, she was found at the bottom of the ocean.

One of the main things that they had to do in training,

was to cut the amount of time that it would take them to get to the surface,

and get that plane off, so they could hide that submarine again.

'All attempts to lift the submarine failed,

'so no-one's absolutely sure why the M2 sank.

'She's still lying 30 metres below the surface,

'just as she was almost 80 years ago.'

'As we descend the line, it soon becomes obvious we've got a problem.'

'We've dived into a thick bloom of plankton.'

So where is the ship?

Here we are and we've made the M2,

but, my God, we could be anywhere.

But anyway, there in the murk you can see...

Oh, I've lost it.

Frank to surface, Frank to surface.

We cannot see a thing down here.

I'm afraid we're going to have to call this off. Over.

'OK. Got that, loud and clear. Thank you.'

'It's a huge disappointment,

'but the M2 has intrigued me for too long to give up now.

'I'll be back when the water has cleared.'

We were here three weeks ago and the visibility was just terrible.

We could hardly see our hands in front of our faces.

But the word is that the plankton bloom has died off

and the visibility has cleared right up.

Hopefully this time we can see something and have a look around.

OK, I've got a lot more vis now.

Wow, here she is, looming out of the murk.

Absolutely wonderful.

The scale of the thing takes your breath away.

Magnificent.

So, this here is the periscope.

And here is the conning tower

where the officers would have stood when the submarine was at the surface

and they'd be scanning the sea.

And then when the time came,

they would give the order to launch the airplane up in the sky.

'The amazing thing about the wreck of the M2

'is that 80 years after she sank,

'she's almost completely intact.

'Which means the clues as to why she sank are still here.'

Here is the aircraft hangar.

This is where the miniature biplane was stored.

Look at this, it's incredible.

You can see that these doors are still wide open,

this is the prime suspect here for what caused the end of the M2.

These crews were trying very, very hard to make this concept work.

The question is, were they trying too hard?

Perhaps this was opened too fast

when the submarine came to the surface.

As the aircraft was being pushed out,

the sea rushed in,

flooded the interior of the submarine

and sent it down to the bottom where we see it today.

'Many believe the sinking of the M2 was down to human error,

'but it could have been a technical malfunction.

'She sank so fast

'that no-one lived to tell the tale.'

During the attempts to salvage the M2,

all of the access hatches were sealed with concrete.

They only ever recovered two bodies.

So the remains of the 60-odd crew men are still inside.

The M2 is a designated military grave,

it's a steel coffin on the sea bed.

'This unique wreck is a poignant reminder

'of what an unforgiving place the ocean can be.'

Back outside Poole harbour,

the archaeologists excavating the mysterious Swash Channel wreck

are fighting to save her.

They may not know her full story,

but they do know what an important discovery they have on their hands.

It's interesting and important because we've got bits of ship that don't exist anywhere else.

If you were to summarise what you've learnt so far?

We've learnt, since the beginning of this really...

Initially this was quite a small wreck of unknown character,

now we know it's a large wreck, it's high-status, it's in these carvings.

It's built and constructed to trade out to the tropics

in a period when this was something new.

What this ship was engaged in, and other ships like it were engaged in,

is the reason why we have Japanese cars and Chinese videos.

So actually, in world-history terms, this is an important object.

But you are now engaged in this race,

because this thing is deteriorating fast, right?

So you're in a big, big race.

We've watched it fall apart in front of our eyes for five years.

But you can only do one thing at a time.

'With such rapid deterioration,

'there's pressure on the team to preserve the ship.

'And the basics of preservation are a lot simpler than you might think.

'Some of the wreck can be covered up

'and protected for the future.'

What happens is all the sediment finds its way into the nooks and the crannies between these sandbags

and that actually forms a seal.

It might sound a bit rudimentary, but it actually really works.

'And what can't be covered, can at least be recorded.'

What you can do is take pictures of exactly what the sea bed looks like

and build that up into a sort of photomosaic.

And I do row after row after row,

so that all is not lost -

when this wreck is physically gone,

the information isn't.

'Ultimately, the best way to preserve a shipwreck

'is to lift it from the water altogether.

'But the expense and logistics involved

'make that almost impossible.'

'But remarkably, that's just what's going to happen

'to large parts of the Swash Channel wreck.'

We're going to raise the first 12 metres of the bow,

the rest of it, we're going to bury in situ and leave it there.

But to you archaeologists, it seems quite routine.

Let's chop it right off and bring it up. In archaeological terms, that's probably quite normal.

No, it's not normal at all!

-It's completely extraordinary, no-one's done it for 30 years.

-Wow!

Last time in Britain it was in the Mary Rose.

It's as extraordinary as I thought then!

Raising the Swash Channel wreck will be an arduous task

which Dave and his team will attempt later this year.

There's still a long way to go

before we discover all of the secrets of the Swash Channel wreck,

but due to the painstaking work of the archaeologists,

she has now been revealed as one of the most important wrecks in our waters.

This series has revealed the secret world

that lies beneath Britain's seas.

I've never seen anything like this,

I'm just being surrounded by dorsal fins.

Uncovering our magical marine life, mysterious wrecks,

and our ever-changing relationship with the sea.

These are what we're after.

Look what else has come up as well!

Our native waters are every bit as dramatic,

colourful, and surprising

as any of the oceans of the world.

You can really get a sense of how fast they hit the water

and stun those fish!

Subtitles by Red Bee Media Ltd

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