The Wild North Britain's Secret Seas

The waters round 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.

Three, two, one, now. OK, that's them firing.

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.

There's a vast amount of stinging power in those tentacles.

Journalist and underwater archaeologist Frank Pope

will examine the bigger picture of our relationship with the sea,

and explore our maritime history.

We are coming up the starboard side here.

You get a sense of the scale of this ship.

This series will take us on a journey right around our British seas,

to uncover the most startling underwater wonders.

This time we're exploring the waters around Scotland,

home to some of the most rugged and isolated places in Britain.

And that makes these seas perfect for some very special wildlife,

but also for some very secret human activities.

Beneath our waves is a world of secrets.

The waters around our northern shores are wild and cold,

and the weather can change in an instant.

Our expedition begins on a glorious morning in the port of Dunbar.

Scotland is renowned for its wildlife,

perhaps none more so than its spectacular variety of seabirds.

But over the past ten years,

numbers of some species have declined dramatically.

So, around the UK we have lost

40% of our herring gulls, kittiwakes and fulmars in the last ten years.

-That's a vast amount.

-That's a huge number!

-But there is one species

that is doing rather better, and that's the northern gannet.

They are doing exceptionally well in British waters.

That's what I want to get to the bottom of, the fact that our gannets are doing well

when the rest of world's seabirds are in decline.

-Cheers, Frank.

-Bye, guys. Have a good one!

-See ya, Frank.

To find out why the gannets are thriving,

Tooni and I are heading out to one of the most amazing wonders of the natural world.

Just two kilometres offshore,

jutting out of the North Sea, is Bass Rock.

This volcanic outcrop

is the largest single-island colony of gannets in the UK,

and a protected seabird sanctuary.

This is such an unbelievable place.

It is covered in bird poo.

Urgh!

So we're looking at over 100,000 gannets on Bass Rock at the moment,

and come the end of breeding season,

that will be about 150,000 after the chicks have hatched and matured.

-Oh, there's a chick.

-Where?

-A tiny little chick's head poking out.

Yeah, I can see them.

To get a better understanding of the reasons behind the gannets' success,

we've come to the island at nesting time.

The rock is packed with breeding pairs and their chicks.

While I'll be observing them underwater,

Tooni will be investigating on land.

I'll see you later.

The reason for my hard hat is that these creatures are incredibly territorial,

and they defend their space by dive-bombing

and releasing some rather potent ammunition.

As I walk up to the nesting sites,

I'm getting dive-bombed by these fiercely protective animals.

Bass Rock was once inhabited,

but the last lighthouse keeper left in 1988,

and now it's only the seabirds that remain.

Oh, look, chicks!

Gannets mate for life, returning to the same nest every year.

Males and females look identical,

and the only sure way to tell them apart is a DNA test.

But when a male returns from fishing,

he will often grab his partner by the scruff of the neck shake her.

This is like the most visceral, complete, all-sensory experience you can have.

It's noisy, it's smelly,

you're right in the middle of a soap opera of life just happening all around you.

It is absolutely magical!

We're here to find out why the gannets are doing so well,

so while Tooni's on the island,

I am going to make a dive over here

and see if I can find out how deep these gannets dive for their fish.

Away you go, Paul!

Well, I'm hiding under the boat,

because if the gannets see my shape in the water they won't come in,

they'll think I am a predator of some kind.

To draw the feeding gannets closer to our boat, we throw in a few fish.

Yay!

Good one! Look at that!

So, here you go, these birds, they are coming in.

They get that momentum by diving from up to 30 metres high.

So that means they hit the water at about 40 miles an hour,

and if we did that we'd break our skulls,

but they can get away with it because they have got super, super hard heads.

Ah, that was a beautiful one.

Gannets are built to dive.

As well as their tough skulls,

they have special air sacs in their chest

which act as mini airbags to cushion the impact of hitting the water.

Wow!

I'm right here at six metres deep,

but I can see the gannets going right down to about 20 metres.

The gannets dive much deeper than other birds,

so therefore they stand more chance of getting more food.

It's pretty good watching these guys so close. You can really get a sense

of how fast they hit the water and stun those fish!

Back on Bass Rock, I've joined Dr Keith Hamer

from the University of Leeds.

The adult is looking up this way.

You can't see the chick's head - it's preening itself, I think.

To better understand the birds,

Keith and his team are investigating the gannets' diet.

Nicely done.

But they're not always keen participants.

Keith's research could help us understand

why gannets are doing so well compared with other seabirds.

When they open their beaks, it's then that you begin to appreciate

quite how large and hard those beaks might be.

That's it, good, so get your arms around the wings,

make sure they are tucked in nicely.

And then just keep a decent grip on the beak.

That's an incredible strength.

-Yes.

-All right, I'm not going to hurt you.

It's all in the name of science, I promise.

Keith is retrieving tracking devices that he attached to the gannets

to study how far these birds fly in search of food for their chicks.

This is one of our GPS loggers.

It talks to satellites, and it gives us a very precise location,

so we can build up a track of where the bird's been.

OK, so this is the device we got off a bird earlier,

and what you can see here is the tracks of the trips that it made.

The data shows that in the last week,

this bird has flown over 750 kilometres hunting for food.

Most British seabirds rarely travel

more than 50 kilometres.

So the gannets' extraordinary range must be a factor

in their resilience.

And Keith has found that, when food is scarce,

gannets can fly as far as Norway,

a four-day round trip of over 1,500 kilometres!

The team have also been taking tissue samples from the gannets for chemical analysis,

and they've turned up something very surprising.

So, the feather and blood samples you take,

what kind of information does that give you about the birds and what they are eating?

The main things they feed on

are either these small sand eels close to the surface,

or they feed on predatory fish like mackerel and herring

in the mid-water column.

The rest of the diet is a mixture of species that live very close to the sea bed.

These birds can dive about 20 metres,

but things close to the sea bed are beyond that sort of range,

or they are fish that are just too big

for even a bird the size of a gannet to catch for themselves.

What fascinates me is that from the research that Keith is doing here,

and from what Paul saw earlier, some of the fish that the gannets are eating

actually live far deeper than the limits of their diving abilities.

So we know the gannets are eating fish that swim deeper than they can dive.

We'll be investigating how they do this later on.

Bass Rock is one of almost 800 islands in Scottish waters.

I've travelled just over 300 kilometres

to visit another rocky outcrop,

located off the most north-westerly point of mainland Britain.

This is one of the most sparsely populated areas in the country.

And it's just as well.

Here at the north-western tip of Britain, it's so remote

that for the past 100 years, it has been used as a bombing range.

And over there is Garvie Island, which is about the size

of a medium-sized aircraft carrier, so it makes an ideal target.

And this is the only place in Europe where you can drop live 1,000lb bombs.

The sheer number of bombs dropped on Garvie Island every year

mean that some of them inevitably fall into the sea,

and some of those fail to explode, which makes this place

the ideal training ground for one of the most dangerous jobs in the military -

bomb disposal, underwater.

Royal Navy divers come to these cold and turbulent waters each year

to clear away unexploded ordnance,

and it's a vital part of their training.

I've joined Lieutenant Commander Jason White

to find out how to defuse bombs under the waves.

Underwater bomb disposal in some ways is probably easier than doing it on land.

I was out in Iraq, we've got teams currently in Afghanistan as well.

At least you've got no-one shooting at you underwater.

It's all about getting the diving side so squared away that you're not really thinking about the diving.

You get the diving to the point where that's just a way of getting to the job.

So what kind of bombs are they?

We've got mixed down there. We've got 1,000lb bombs, we've got 250kg bombs.

Yeah, a 1,000lb bomb,

if this thing went off underwater,

while we were working on it, if we're up close on it, we're gone -

-is that right?

-Fish food.

Bomb disposal is as complicated and dangerous underwater

as it is on land, but at Garvie,

the Navy divers also have to deal with cold waters and raging currents.

On the Navy support ship, the team are preparing the explosives and detonators we'll be using later on.

-That's really precise work, this isn't the sort of thing you want to screw up, is it?

-No.

-Yeah, exactly.

I've worked with explosives in Antarctica, so I've got a licence to use them.

But I've never done it underwater.

The sea bed around Garvie Island is littered with unexploded bombs,

but amongst the kelp, they can be very difficult to find.

Navy divers take on many challenges,

from underwater bomb disposal to rescuing submarines.

And they get to use some seriously cool kit.

As you can see,

we're wearing very different diving equipment.

You can see that Ginge is wearing this gear that makes no bubbles,

it's called re-breather equipment, it's completely silent.

There's a reason for that, and one of them is that some live bombs

can be activated by noise, they're acoustically sensitive.

These bombs here are not acoustically activated,

which means I can wear the lighter,

easier-to-use open circuit, so I can make some bubbles quite safely.

Ginge's rebreather removes the carbon dioxide and recycles oxygen,

which means he can stay down for longer looking for bombs.

Oh, yeah, look.

Found a bomb!

You see, you can swim right past them, and I just did -

I thought this was a rock.

It's a whopper. What do you think, mate?

Oh, keep away from it? OK.

Ginge has given me the sign, he's not sure about this one.

He's declared it a live so he's given me the hands-off signal - if that thing went off,

we'd be in big trouble.

The bomb is live, but once he's examined it and determined the risk,

Ginge is happy for me to return and help him tie a buoy to it.

We're going to mark this now with this rope, that way we will know

exactly that when we come back down this line, that we'll be coming exactly to this bomb.

Good one. Thanks, Ginge.

With the bomb's position marked, we return to the surface

to collect the plastic explosive we prepared earlier.

I'll tell you what, that was great!

You want to get yourself aside a 1,000lb bomb to get the blooming juices flowing!

A bit sobering as well. You can't mess around with this stuff,

absolutely can't mess around with it.

Diving back down the line,

we've now got to secure the plastic explosive to the bomb.

Not an easy task when it's embedded in the sea floor.

Got it.

I can't get to that end.

So we're going to get a sandbag sent down from the surface to plant on top of here.

You see, it's hard work, because not only are we swimming around

with live explosives, we're also dealing with this really strong current, look.

The current's going that way, it's like a steam train.

Here's the sandbag.

Brilliant.

It's going to make life easier.

Ha-ha! Thanks, mate! That's it.

It's ready to go.

Time for us to swim away, I think!

Ha-ha! It's a great place to be - but not for much longer.

Just line it up there, Paul...

Safely back on the surface, we need to ignite a fuse that will slowly

burn underwater, all the way to the explosive we attached to the bomb.

OK. Three, two, one, now.

OK, that's them firing.

-Now you unscrew them.

-Yep.

That's burning now. That's alive now.

This is the point of no return.

It's time we left!

Fuse is burning.

-How long have we got?

-Five minutes.

-We've got five minutes, OK. How far away do we have to be?!

-Er, well, as far as possible, really.

Yes! See? If we're going to use that as the bull's-eye for the...

most bombed place in Europe, then we have responsibility for cleaning up the ones that didn't explode.

These are the ones to do it. Pretty exciting stuff. Thanks very much.

-OK, no problem.

-I'm all fired up!

Despite periods of intense bombardment several times a year, military activities and wildlife

have co-existed in the Cape Wrath area for over 70 years -

largely because people are kept away.

But you don't need to go somewhere this remote to see some very special marine creatures.

The wild coast of Scotland is home to some of Britain's biggest marine mammals.

Orca, minke and pilot whales can all be spotted here.

It's also the home to many people's favourite sea creature, the dolphin.

Britain's largest resident population

of 130 bottlenose dolphins live in the Moray Firth,

just north of Inverness.

Many will stay here all year, whilst others will travel down

as far south as the Firth of Forth,

tracking schools of salmon and mackerel along the coastline.

Their acrobatic displays have made these north-eastern waters

a magnet for dolphin watching,

contributing over £4 million a year to the local economy.

The ones here are a lot bigger and fatter than the bottlenose dolphins

in, say, the Caribbean, Indian or Pacific oceans because they need this thick layer

of blubber to keep them warm in the cold waters of the North Sea.

How do dolphins keep their family pods together?

Intriguingly, it might be by using an equivalent to human names.

As human beings, we know if we're being called,

irrespective of who is calling us, because we recognise our own name.

Between the ages of one and two years, bottlenose dolphins

create their own unique sound, known as a signature whistle.

But is it a name in the same way we understand one?

Stephanie King, a zoologist from the Sea Mammal Research Unit, is researching this.

They have been studying the calls of dolphins in this area since 2003.

So what's the aim of this research you're doing in the Moray Firth?

Well, we know dolphins use signature whistles to communicate with one another to broadcast their identity,

and we know that they sometimes copy each other.

So they'll copy one another's signature whistle - and we really want to know why,

what's the function of them copying another dolphin's signature whistle?

It's believed dolphins may copy each other's signature whistles

in order to address one another.

To find out, we'd need to show that a wild dolphin can recognise

its "name" and respond to it.

And if they can, they would be the only animal apart from human beings

that are capable of doing that.

Working with wild dolphins is challenging.

They're constantly on the move,

but it's essential that Stephanie can identify the animals she's working with.

So we want to take photos of the dorsal fins of the animals -

and this is how we can track individuals.

They have certain scarrings and little tears, which we call nicks, along the fin.

-You get very familiar with what animals are out here?

-Yeah, you do.

There they are.

Literally all around, aren't they?

It's hard to differentiate between different groups.

So try to keep those animals in sight, let's not lose them.

Dolphins don't generally make their signature whistles

when they're travelling, so we have to stay with the group until they begin socialising.

To find out if they're whistling, we'll listen using a special underwater microphone

-called a hydrophone.

-Now we're going to put the back hydrophones in.

-OK.

-So if you grab the one on the port side, I'll go to the starboard.

Any sounds that the hydrophone picks up will be recorded to a laptop.

Lots of clicking. Quick, quick, quick, they're whistling!

You picked them up on the hydrophone?

-You heard them whistling almost instantly?

-They were whistling a lot.

It's quite exciting when you pick up some recordings, because sometimes they can be quiet for hours.

-Do you want to hear?

-I'd love to.

So this is a dolphin signature whistle.

HIGH-PITCHED WHISTLING

That's a really lovely sound!

This is the sound of one dolphin making his own signature whistle.

But we need to play it back to him as if it came from another dolphin.

Our first step is to create a computer-generated version.

So it's exactly the same whistle but we take away all the voice features.

So it's like another animal calling the dolphin.

And then we play it back through the loudspeaker.

We need to be able to see how our dolphin pod react when they hear the modified whistle.

But we can only do this when they're near the surface.

OK, great. That's our group!

-Nine o'clock, 300-400 metres.

-Straight into the water.

Speaker in...

Animals still at 12 o'clock now.

-Playback.

-Stephanie only plays the signature whistle twice

and observes their response.

-Are they still up?

-Yep.

OK, half past two, three o'clock animal, this one's a bit closer now than the others.

The others are 120 metres,

that animal's about 80-90 metres.

Jumping.

Interaction. Jumping backwards...

At the same time, the underwater microphone is recording any sounds the dolphins are making.

The results of the team's research have been intriguing.

The dolphins appear to be recognising their own whistle and calling back.

Right, so this is what we recorded earlier.

So here we have the playback, it's a very clear signal.

And then we see the fainter ones are the responses of the animals.

And you can see here we have the playback sound

and then the animals responding -

and there's a copy of that whistle.

-It's very, very clear.

-Mmm, very clear, and not just that but

the other animals are responding, they also call their whistle.

As well as whistling, the dolphins in the pod have swum towards the underwater speaker,

which suggests they do recognise the call or "name"

as being that of one of their group.

So is it like if we were in a darkened room, and in order

to assess who was there, we'd all call out our own names,

so everybody would know where everybody else was?

Yeah, exactly, instead of calling out names of other people, you would call your own name.

I'd be calling, "Stephanie, Stephanie", you'd be saying, "Tooni, Tooni".

And that way we'd know who's there, we'd come back together and join up again.

It makes more sense in an underwater environment,

if you're not sure who's there, to broadcast your own identity,

to bring the group back together, rather than calling other animals' signatures at random.

As well as calling their own name, the dolphins will also copy

the signature whistle of others in their group.

Stephanie's work has begun to show that when a dolphin hears

its own signature whistle, it responds and calls back.

When Stephanie plays them a whistle from a dolphin they don't know, they don't react.

With the controls, the whistles aren't that different, but they don't respond.

-These dolphins just recognise the whistles of the animals they associate with.

-That's fantastic!

So each bottlenose dolphin has a name that it develops itself,

and that the others in its pod recognise.

And dolphins seem to be copying each other's names in order to call one another -

which means dolphins are the only animal, other than us,

that have been shown to use names in this way.

Stephanie's research is just the tip of the iceberg.

It could not only help us understand the evolution of language,

but could also give us an insight into the complex existence

of a highly intelligent mammal.

The North Sea may hold many more secrets.

From better understanding the creatures that live there,

to offering resources that could unlock new ways of treating disease.

One of the myths of undersea Britain is that it's dull, lifeless

and there's not very much to look at.

Tooni and I have come to St Abbs.

The area is a marine reserve.

It benefits from a flow of Atlantic water entering the North Sea around

Scotland's northern tip but also from a cooler Arctic influence.

Because of the strength of the water rushing down,

there's a huge amount of nutrients and life going on down there,

-so it should be a really exciting dive.

-Oh, yeah, I'm in.

I'm in! We're here to reveal that our marine life is not only more colourful than you'd imagine

but could also help in the fight against cancer.

Wow!

St Abbs is such a special dive site because there's such a diversity of life here.

Not only are there the kelp forests beneath us,

but there's also these giant expanses of rock face

that provide a hard substrate for all of this marine life to colonise.

Water filters out sunlight.

The deeper you dive, the more colours disappear.

But with our torches, we can put the daylight back

and reveal the magnificent creatures as they really are.

This wall is pretty fantastic, Tooni, look at it.

And there's no shortage of beautiful natural colour, is there?

Yeah. Actually, whereas things look quite dull, once you shine

-your torch on them, it really picks out the reds.

-Even these urchins are beautiful.

You take your light away and they're just black and white.

You put your light back, and look at the colours!

Those wrasse are very inquisitive. That's a classic case.

He looks really brown and murky but when you shine a light on him,

you can pick out his red colouring.

Not every creature wants to be seen.

You wouldn't even notice some marine life unless it moved -

like this lemon sole.

Ah! Look at him! Ha-ha!

He's using his colour to camouflage himself, isn't he?

Absolutely.

Animals use colour underwater

in almost exactly the same way as they do up on land.

So there's camouflage to blend into the surroundings,

to signal to a mate, or to advertise

that they're maybe poisonous, they use these bright reds and yellows.

Well, if you had to pick one single dive in British waters

to dispel the myth about what's really under the sea -

is it dull, lifeless, is it not very interesting, and not very colourful?

Then this must be the dive.

But to see how colour may offer help in the fight against cancer,

we have to come back at night -

to see something that's normally beyond human vision.

Scientists think that some marine animals can see colours far beyond those that we can.

So we've come back to our dive site at night

with some special equipment in order to reveal some of the secret colours

of the underwater world.

OK, well, let's go see what go and see what we can find, I guess.

Wow! All the anemones are out feeding.

So many crabs out!

Many marine creatures can see beyond our visual range -

some even fluoresce.

For us to see this, we're going to need blue lights,

and special orange specs.

Right, so this is the barrier filter going on,

which is the slightly forensic-looking yellow mask.

This is the blue light which we'll shine onto the marine animals

to actually see if they're emitting any of the fluorescence.

Ah, Tooni!

Tooni!

Oh, wow!

God, it completely springs out at you!

The combination of blue light and orange filters allow us to see

this extraordinary phenomenon -

something that's never been filmed before in British waters.

Now these anemones, it's thought that they actually fluoresce

because their main prey item is cocapods,

which live in the plankton.

And cocapods fluoresce to attract a mate,

so it could be that the anemones have evolved

this fluorescent protein to get their prey to come to them.

Oh, wow!

Just look at that!

That is some fantastic colouring.

It really jumps out at you!

That is just absolutely beautiful, isn't it, Tooni? Look at it!

That's fantastic!

They're called lightbulb sea squirts.

And the way in which they feed, and why they're called squirts,

is because they pump water in one way, extract their planktonic food,

and then pump the exhaust fumes, as it were, out the other way.

Everything's fluorescing! Ha!

Scientists have identified the gene

that produces the fluorescent protein in marine lifeforms.

And intriguingly, this discovery has been used

to help study cancerous cells.

Basically some cellular processes are really hard to see

because they're so microscopic. These fluorescent proteins

are actually used to mark this, so it's a lot easier to see.

The fluorescence acts like a marker in the cancer cells,

allowing them to be studied and precisely tracked.

So there's a lot of research at the moment in deep-sea biology

to try and find more marine organisms that fluoresce.

That's fantastic work.

What a brilliant part of the ocean eco-system.

And it's the potential for scientific advances such as these

which makes it so important for us

to respect the seas and marine life that surround our own island.

-Good one?

-Yeah, that was great. What a way to end the dive, hey?

It's pretty special going down on a night dive and coming back at dawn.

Look at that.

People always say there is so much to discover in terms of human health in the rainforest,

but it's exactly the same with everything under the ocean as well.

Down here on the east coast of Scotland there're things

you can track cancer cells with. I think that's amazing.

Here at Bass Rock, Tooni and I have been investigating how gannets can be doing so well

when other seabirds are in decline.

And Frank's out there on the ocean

looking at how fishing is affecting seabird populations.

We're on the Launch Out, which is a trawler that's fishing for prawns

off the east coast of Scotland.

Prawns, as Scottish fishermen commonly refer to langoustine, live in burrows on the sea bed.

Trawlers catch them by dragging huge nets along the bottom.

The skipper on this trawler is Jim Wood.

How long have you been doing this?

I've been in the wheelhouse for 32 years.

In the wheelhouse for 32 years?

My father got this boat built in '67

and my grandfather, he was a fisherman before that,

and my great-grandfather before that.

I don't know any further back than that. Four generations anyway.

-Pretty safe to say they were fishermen too.

-Probably. Aye.

-And always fishing for prawns or what?

-No.

For the first 20 years, it was mainly fish. White fish, mainly. Haddock.

-Plaice. Sole.

-And then what happened?

The fish took off.

-So we've landed prawns for the last 15 years.

-So the fish moved out?

The fish have moved away from this area. Yeah.

Whether the fish have moved due to warming waters pushing cold water species away,

or simply because we have fished out the area, is still open for debate.

But the change in the amount, and types of fish available,

has dramatically affected some seabirds.

And commercial fishing techniques have also had a direct impact.

In the North Sea and the Baltic,

there are some 90,000 birds that get killed every year in fishing tackle.

That's quite a big problem.

But somehow, gannets are thriving against the odds

when other seabird populations are in decline.

And I think I know why.

Did we catch anything?

Wow!

So look at that. There's a fair amount of prawn in here.

These are what we're after.

Look what else has come up as well.

All the crabs. That's a dab.

Look at him, he's a murky-looking fellow from the deep.

Anything else, James?

A huge proportion of prawns but there are other things in here

and this is what you call the by-catch.

By-catch is the name given to any marine life unintentionally caught.

Every year in the North Sea,

fishermen net around 900,000 tonnes of by-catch.

That's the equivalent of about 120,000 Route Master London buses.

By-catch is strictly regulated by the European Union.

Any animal deemed too small or outside your quota,

has got to be discarded.

But most of it will already be dead by the time it's thrown back.

This terrible waste provides a feast for the waiting gannets.

These offshore trawlers offer a fast food supply.

But of the British seabirds, it's only the gannets that have the incredible range that allows them

to fly the hundreds of kilometres to where these boats often fish.

So the gannets are able to eat fish that live deeper than they are able to dive

because the fishermen are catching it for them,

and they are throwing their unwanted catch over the side.

The gannets are greedy opportunists,

a bit like urban foxes, and they've adapted to eat pretty much anything

they can get their beaks on.

So, the gannets' varied diet has certainly helped them

buck the trend of declining seabird populations.

In fact, they've been so successful here on Bass Rock that it has reached capacity.

There is simply no more room for any more birds.

While this rugged and desolate coastline may offer a safe haven

for seabirds, it's been the undoing of a great many ships.

We've come to the Sound of Mull, off the west coast of Scotland.

For centuries, these waters have provided a cut-through for shipping.

But bad weather, rocky outcrops and warfare have lead to numerous wrecks

lying at the bottom of her clear waters.

Frank and I have both dived a particular wreck here before,

but we've returned to see how much has changed,

and how we might protect our maritime history.

There are over 25,000 shipwrecks recorded in British waters

but they are slowly being lost to us.

Not just by forces of nature, but also because of human activity.

This is the Breda, a Dutch cargo ship.

During the Second World War, she was carrying supplies to British troops,

everything from shaving kits to bi-planes.

But on 23rd December 1940, enroute to Mombasa,

she was attacked by a German bomber.

I was first here in '82,

and I remember coming back from the US.

I was nine years old.

-Oh, I love it. Were you 9?

-So what did you see in '82?

Well, I remember the decks being strewn with stuff.

You could go down, find this, find that,

find great big brass things, and you know just get amongst it

and get stuff home and put it on your mantelpiece or something.

Increasingly among the dive clubs, people say don't take anything,

because you are spoiling it for everyone else,

you're spoiling it for the historians and for the other divers

but was there any kind of that sense when you dived it?

No. No. There wasn't. Very much the opposite.

There was a keenness, amongst everybody,

to bring up to the surface as much as you possibly could.

I've got a treat for you.

Here's what I looked like when I dived this thing in '82, are you ready?

-Oh, my God... Let's have a look!

-You need to brace yourself.

That's what I looked like.

It's Burt Reynolds!

One of the magical things about diving a shipwreck is that you get a sense of stepping back in time.

But of course wreck diving can be dangerous. Our dive supervisor,

Richard Bull, is laying out strict ground rules.

This is a union dive. What that means is one out, all out.

If one person has to bail, we all come up.

Since I last dived the Breda in 1995,

three people have lost their lives exploring this wreck.

Two people with collapsing material, right?

Well, let's not get into those situations.

Just because it is underwater doesn't mean those large lumps

are not affected by gravity.

They come down, all right? It would spoil the whole day if we...

-Lost somebody.

-Had to deal with something very unpleasant like that.

-Got that one?

-Deal.

-No heroes, right. Deal.

Down we go, mate. Here we go.

We're here to see how much has changed on this Second World War cargo ship

since Paul first dived her nearly 30 years ago.

I love this moment, when the wreck first appears out of the gloom.

It's a lovely feeling, isn't it? We're back on the Breda!

-Wow.

-So we are coming up the starboard side, here.

You get a sense of the scale of this ship.

Ah, OK, look down, look down here.

This is probably the main hold here.

This must be hold number four, Frank.

Probably. This hold is about three storeys high.

It would once have been full of cargo.

Whilst a lot of the cargo was salvaged at the time

and some of the artefacts will have naturally rotted away,

what's striking here is just how little remains.

This site used to be full of...

all the paraphernalia of living in the 1940s.

Holy smokes, it does look a lot different!

It's a very different shipwreck to the one I saw in 1982.

There was just a lot more stuff around.

A lot more boxes and discarded tools and equipment.

But now look, it's all gone.

It's been picked clean.

It's been picked clean by the hundreds and hundreds,

probably thousands of divers that have been here.

Since the early days of diving, we've had to report all finds to the maritime authorities.

But while it was once common to pick up souvenirs,

we've now got a much greater appreciation for wrecks

as historical sites that should be kept intact.

What's so important here, Paul, is to remember

this is a museum, really. If each one of us takes one souvenir,

pretty soon that's it, and there won't be anything left to give the sense of the people

who sailed on board her.

Fortunately there are still a few large pieces left on board

that remind us this was a cargo ship on her way to the frontline.

Tyres, wheels. Oh, yeah,

this is a big four-wheel-drive truck.

Look, you can see the differential here.

Ha-ha, yeah.

Well, that's it, I'd love to spend a lot longer on this lovely shipwreck,

but sadly, it's time for us to go.

Five divers on the surface, aren't we happy, people!

Five went down, five came back.

It was a good day.

It would be hugely expensive to raise and protect a wreck like the Breda,

but new technology may allow us to preserve her in another way.

In fact to experience her you won't even need to be a diver...

This is really cutting edge, now.

This has been surveyed in a way that not many wrecks have been.

To capture the wreck before she decays any further,

the Breda has been surveyed using technology developed by the oil industry.

A sonar scan has created a high resolution, three-dimensional image.

You see, she's got these weird goal-post shaped masts.

Can you see the rugby posts laying down on the wreck there?

-Look at that detail.

-Gosh, this is just a fantastic program.

-I just love the fact that you can see inside it.

-Yeah, it's great.

This is a wreck that's changing over time, as the metal rusts,

as the wooden deck rots and run that change for a few hundred years

then you end up with just the real skeleton of the ship.

With new technologies, we can create permanent archaeological records,

and digitally preserve some of our most significant shipwrecks.

This is a lovely combination - we've got this great remote sensing tool,

and we can monitor what's going on and see changes, yet we've still got the personal engagement

that we all want as divers, and that's to swim down there,

have a look, and really connect with it.

And we don't literally have to pick stuff up, and stick it on our mantelpiece,

your point's well made and I'm converted.

Our northern waters contain a wealth of maritime history from WWII wrecks,

to 17th-century merchant ships,

and all of them can inform us about our past.

And to understand what's happening in the sea today, we're using even more surprising methods.

I'm on my way to meet a vet who's got a bit of a mystery to solve.

There's been a body washed-up on the beach.

No-one knows the cause of death.

I've come to Inverness, in the Highlands of Scotland.

I'm here to meet the team that investigates any mysterious casualties

that wash up along the coast.

The Wildlife Unit at the Scottish Agricultural College

is responsible for investigating some marine deaths.

-Now then, hiya, Bob.

-How are you doing?

'To determine the cause of an animal's demise, the team perform an autopsy.'

They conduct around 75 every year

on creatures ranging from leatherback turtles to whales.

Their work is crucial in helping to monitor what happens in our seas.

Their results could reveal anything from an outbreak of disease to marine pollution.

Wildlife pathologist Dr Andrew Brownlow will be performing today's autopsy.

Look at this beauty.

It's still a beauty, even though it's a bit sad looking.

This bottlenose dolphin was found dead on a beach near Aberdeen.

But the question is, what killed it?

Even before we pick up a scalpel blade there's things that we can see

just from looking at the outside.

What we've got here are these sort of leaf-like marks.

-Oh, yeah, what the heck is that, then?

-Bird peck marks.

Ah! So then the birds get on them pretty early, I suppose.

These rake marks on the back here, these cuts that you can see here.

And we think these are from other bottlenose dolphin.

So you can see...

-a strip here.

-Dolphins are known to attack porpoises

and occasionally have been known to attack their own juveniles.

So we're going to use a jaw bone for comparison.

-They match-up fairly well.

-Oh, wow.

So, they are about 11mm apart, which is, roughly speaking,

the distance between each one of the teeth.

Yeah, look at that. You can imagine that giving it a good old scrape.

There are other, similar markings on the dolphin

but are these wounds significant in understanding the cause of death?

You can see that this one has begun to heal,

there is a little bit of evidence of scar tissue around it.

It's very vague but the chances are that didn't happen at the point at which this animal died.

From the condition of this animal, we will be able to tell when we actually do the post-mortem,

but it looks like he's in fairly good nick.

How are we going to unravel this mystery, then?

Well, it's not an exact science.

It's little bits of evidence you put together, this and this, and gradually build-up a picture.

It's not a "that's what did it".

I bet. He's pretty heavy.

From the dolphin's size, Andrew can tell he is less than a year old,

so he definitely didn't die of old age.

I'll take a strip off the back so we can measure blubber thickness.

OK. What can you tell by measuring the blubber thickness, then?

Condition. Basically. Whether or not it's been feeding,

I mean, the blubber is an amazing organ,

it has an insulative capacity - it's energy storage.

What does your instinct tell you straight away?

That it's not as thin as some of them that we've seen,

where they've got no reserves, but it is on the low side.

From the state of the blubber, it appears that this dolphin

was not in good condition at the time of its death.

Actually, you can have a go at this.

Yeah. I'll have a go. Dead right.

The bottom bit of this line is probably about level with the spine

so all of this is muscle, this is the powerhouse,

this is what's required to get the propulsion through the water.

Right. This is the engine room I'm coming into, then.

This is the bit where if you are doing this on a big whale,

everyone is standing back because this is the bit that explodes.

Oh, I see. I can imagine, actually.

Nice. That's really good.

You can see the organs, we've got the kidney here.

Yeah. Look at that liver there as well.

-That's the liver right?

-Absolutely. You can do my job.

I'll go get the coffee.

Each one of the dolphin's internal organs are removed

and examined, but they all appear to be normal.

Further laboratory tests confirmed this.

-There we go.

-Fantastic I'm holding one set of ribs.

Removing the rib cage may reveal broken bones, evidence of trauma

that led to its death, such as being hit by a boat.

Feel that. No fractures.

Oh, I see. That's clever.

So what we're checking for...

So you can see in there if there is any injury to that at all and there is none?

There's nothing broken so it's unlikely to be a trauma case.

OK.

The next stage is to check the stomach contents for more clues.

-Absolutely empty of food.

-It hasn't been eating.

-It acutely hasn't been eating.

-It probably means it hasn't fed for at least a few days.

-At least a few days. Right.

-It's a bit suspicious, something's not looking quite as rosy here.

Maybe it wasn't quite in as good condition as we thought it was.

-So the plot thickens.

-Yeah, I'll say.

I'm going to try and take the entire respiratory system out.

An examination of the lungs reveals this young dolphin was still alive when it stranded on the beach.

What happens is they come in, they are not too good but they are still alive, they fall onto one side.

So you end-up with these asymmetric lungs, one will be probably smaller than the other.

If you see that, you get the idea that it's a live stranding.

So the animal's come onto the beach alive, and then it's died there.

So we now know where he died.

-But we still don't know why. Next?

-So we've got here now...

Oh, wow, feel that! That's amazing.

What am I... What is it? A great, hard, curved lump.

Right what you should be feeling here is the back

of a completely smooth, completely flat and completely non-indented

ventral column of the spine. What you're feeling is...

-A whopping great U-bend almost.

-Is a big dipper.

This is absolutely amazing.

This is nuts. We do not...

-I mean I've never seen anything like this before.

-Right.

Andrew thinks he now has a complete picture of the circumstances

surrounding the dolphin's death.

I'm fairly confident that this seems to be a young animal that maybe got separated from its mother.

-The stomach was empty, it wasn't managing to feed properly.

-It's all coming together.

This huge deformity is most likely the reason it live stranded, simply

because it was unable to keep up and it was unable to swim.

Right. Thank you very much.

Well, there's a mystery solved.

We know this young dolphin died stranded on the beach

and we know it has a massive spinal deformity.

And we think it's likely that when he left his mother and started to look after himself

he couldn't keep up with the pod and when he got into trouble, he couldn't get out of it.

Back on Britain's North Sea, our expedition to understand the success

-of our gannet population is coming to a close.

-It was fascinating.

We went out with the trawler.

When the catch comes on board, of course it's not all prawns, it's other stuff there,

and the fishermen are chucking it overboard and what's eating it? It's the gannets.

That ties in exactly with what we were talking about with the scientist on the rock.

What their results are showing is that the gannets are feeding on fish

that live far deeper than they can actually physically dive.

-Because the trawlermen are bringing it up.

-Precisely.

I really love these gannets, they are adapting to whatever food is going and I say good on them!

The fact that the gannet population is doing so well now doesn't quite mean their future is secure.

These chicks were born about five weeks ago and they need to put on weight quickly

because come August, their first flying experience will be when they take a tumble off this rock.

It's a tough start to life for a gannet, so much so that three quarters of these chicks

will die before they reach independence.

But life could be about to get even harder for these chicks.

The European Union is considering introducing new legislation

banning fishing trawlers throwing their by-catch back into the sea.

Gannet research scientist Dr Keith Hamer is concerned.

Do you think that's set to have a negative impact on the gannet population?

That's one of the things we are concerned about for the future.

If birds have to be away that little bit longer, that might mean chicks

might start being left unattended more and more.

If the chicks are then left unattended, what the non-breeders

will try to do is move in and attack the chick and kill it and then take over the site.

And the danger is then that attacks by non-breeders could start to become a serious problem.

So, in the immediate future, the gannet population here on Bass Rock

might well suffer if the EU enforces a ban on throwing back by-catch.

But in the longer term, any measures that help fish stocks recover

will benefit not just the adaptable gannet but the wider seabird population.

Gannets are thriving because they've made smart adaptations to the forces of nature and the impact of mankind.

And they've done that by flying further and diving deeper.

And last but not least are their fabulous opportunistic feeding habits.

Next time on Britain's Secret Seas, we uncover the power of the east.

Pitting a free diver against the natural ability of the grey seal.

Look at the smooth, efficient way that she's moving, moving just as the seals do.

Harnessing the force of the wind...

The winds here are twice as strong as the global average.

And getting to grips with the future of our lobsters.

It's like they are just wielding these two massive boxing gloves!

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