The Riddle of the Tides Coast

Coast is home.

We're back to explore the most endlessly fascinating shoreline

in the world - our own!

The quest to discover surprising, secret stories

from around the British Isles continues.

This is Coast.

For as long as we've gazed

from our island shores over the seas,

we've struggled to solve

the mystery of our tides.

Twice a day, like the chest of a sleeping giant,

the sea heaves up and down,

re-drawing the shape of our island home.

The effect of the two tides varies around the coast.

In the Bristol Channel,

we have one of the greatest surges of water in the world.

It creates the remarkable Severn Bore.

Over in East Anglia in the south-east corner of England,

the tides are relatively weak.

Down here on the south coast, the opposite is true,

because the tides get forced up and down the English Channel

around a promontory called Portland Bill.

You get huge standing waves there. It's really scary.

Why does the sea behave so differently around our coast?

We're here to explore The Riddle Of The Tides.

My tidal odyssey takes me to the North West,

and a city that sits by the sea.

In Liverpool, I'm on the trail of a forgotten genius,

who made a machine to calculate the tides anywhere, anytime.

Look at that, lots of brass, cast iron, steel axles,

absolutely stunning, isn't it?

In the balmy south, there's an island that puts on a spectacular

tidal show.

At a fortress that floods twice a day,

Miranda is mega-rockpooling in Jersey.

This has to be the weirdest thing I've ever done in a rock pool.

And there's actually a little brown shrimp just sitting on my hand,

feeding off little bits of skin.

On the east coast,

we explore the ebb and flow

that drove beach fashion at Britain's first resort.

Scarborough is where we hide at low tide,

and the Victorian bathing hut rides again, for Lady Tessa.

-Has the horse had enough?

-Yeah.

-I don't blame her. Do you?

-No.

But my journey begins on tidal rapids. The Menai Strait...

..a narrow ribbon of wild water.

Mariners have always been at the mercy of the tides.

Trying to master those turbulent waters

was a great voyage of discovery.

I'm setting sail on this 19th-century-style schooner...

Shall we put it up, Scott?

Yes, go for it.

..to see how salty seadogs began to tackle the riddle of the tides.

Good work out, isn't it? Earning a living.

It's all hands on deck as we rush to set sail

before the tide turns against us.

Proper old ropes that takes the skin off your hands.

A tricky passage awaits along some of Britain's most treacherous water.

Navigating the Menai Strait isn't for the fainthearted.

We're racing to make it through The Swellies -

the tidal surge around the island of Anglesey.

Any misjudgement of the tides here could wreck the boat on jagged rocks.

It's a real worry for the skipper, Scott Metcalfe.

Quite a few people have come to grief.

There's a lot of rocks around here, there's rocks on this side,

and certainly there's rocks on the other side,

the Cribbin Rock, which is quite a nasty one.

If you get the timing wrong

you can get swept onto

one of the rocks, basically.

And this is a, you know, a historic vessel.

How important were tides back in the days before motors?

Very, very important.

I don't know if you can see those two white posts,

we should have those basically in line.

So, you line the two white posts up,

steer for the posts, and that gets you through the deeper channel.

People talk about The Swellies

as if it's some kind of white-knuckle fairground ride.

What are The Swellies?

That's just this stretch of water between the two bridges, basically.

It is the fastest flowing part. This is the most treacherous part.

Scott makes sure to navigate The Swellies at slack water -

the brief period when the tidal flow is weakest.

For sailors, reading the mood of the sea is a matter of life and death.

Since the earliest times,

mariners have known that the moon drives the tides,

but how, exactly?

And why are there two tides a day?

Sailing with me is Tom Rippeth from Bangor University.

Tom, can you explain to me

why it is that we get two tides every 24 hours.

We've got a simple model, here, Nick.

If you'd just like to hold that.

Yes.

This is obviously the earth, and then here we have the moon

and, erm, the earth and moon,

basically, orbit around each other in space,

and erm there's two forces acting, really.

There's one force which is the moon's gravitational pull,

and another force which is the centrifugal force,

which is pulling the water away from the planet.

The earth's motion and the moon's gravity make the tides.

To see how, imagine our planet completely covered in water.

One bulge in the sea is caused by the moon's pull.

There's an opposite bulge because water gets pushed out

by centrifugal force, as the earth whizzes through space.

The earth also rotates, once every 24 hours.

Measure the sea level at a single point

and it rises as the earth spins, and then falls again,

and sea level rises again 12 hours later, so two high tides a day.

But our world isn't completely submerged,

the shape of the coastline and cliffs on the seabed,

like the continental shelf,

disrupt the flow of water, changing the height of our tides.

Our tides go up and down at the edge of the continental shelf,

and that generates tidal waves.

So, we're not talking about a gradual rising

and falling of water every, what, six hours, roughly?

Absolutely not. We're talking about waves

which will travel down one coastline and travel up another coastline,

so, for instance, down the east coast of England,

we'll see big changes in the height of the tide,

but also in the timing of the tide,

so you might have low water in the north,

and you might have high water in the south.

So, our tides aren't simple.

They travel in massive waves,

which makes it hard to predict the sea-level.

Tom's wave tank shows how the tide behaves differently,

depending where you are.

Here we've just put three examples on the Irish Sea.

We've got Liverpool, here, which has very large tides,

and if you move elsewhere in the Irish sea, we actually see

places where it's high water at Liverpool

and it can be low water elsewhere.

So, you can have high water at different times

-in different parts of the coast?

-That's right.

-It's a very complex system, isn't it?

-Absolutely, very complex.

Tides are further complicated by our craggy shoreline,

which makes predicting them very tricky.

But later I'll discover a remarkable machine,

created to crack the puzzle.

But while some probe the mystery of the tides, others work with them.

Along the southern shore of England,

the Atlantic surge is funnelled between Britain and France.

The sea's ebb and flow is the clock for these coastal folk.

At Hastings, the high tide is the fishermen's friend,

allowing them to float their boats off the beach.

But it can mean an early start.

Further west, the way the water sloshes around the Isle of Wight

into the Solent

creates four high tides each day,

double the normal number,

a challenge if you're messing around in boats.

All around the shore, tidal life runs on local knowledge,

like here at Bantham.

The town is home to marine biologist and mum Maya Plass.

Maya makes the sea work for her.

This morning I've got to get my daughter Niamh to school.

Did you brush your teeth yet this morning?

Most parents have to check traffic reports in the morning,

but for me, I check the tide tables.

The tide controls my life here.

Unfortunately, this morning, I've got to take Niamh by van,

but this evening, hopefully, I'll be able to pick her up by kayak

on the high tide.

For Maya, as for most parents, the school run is a frantic rush.

-Sorry, we're a bit late.

-No, you're fine, not a problem.

But she's also rushing for another reason -

she's racing against the tide.

I've got to catch that tidal road.

On the high tide this road is completely covered,

and there will be stretches that will be completely submerged.

You often find people stranded on this bit of road.

Maya's got to get a move on -

while it's still low tide,

this marine biologist mum can free-dive to get her family dinner.

I'm going to hop in and hopefully find a spider crab.

Shallow water means Maya can reach the bottom with one gulp of air.

I've got two females here.

You can tell they're females

because they've got really small claws here.

They've got this big rounded area that's under there

that she'll keep all her eggs,

but we don't want the females.

We want the males - the ones with the nice big juicy claws.

Look at this, he's amazing.

It's a lovely big male.

Look at the amazing size of his claws!

Loads of meat in there.

This one's definitely going to be for supper.

It's time to go and collect Niamh now.

If she times it right, Maya can kayak in with the tide...

The tide time changes every day...

..collect Niamh from school

..so, the teachers are really flexible to the fact that sometimes

I am a little bit late.

And, as the tide turns, get a free ride back.

-Look down here, can you see those cars down there?

-Yeah.

They can't actually get across on this road cos the water's too deep.

But we can. How cool is that?

This morning, she drove along this road. Now, it's become a boat trip.

And soon the tide will turn again, right around our shores.

The routine of coastal folk revolves around the ebb and flow of the sea.

It reshapes their world and opens up new possibilities.

Like on this beach in Cardigan Bay,

on the west coast of Wales at Poppit Sands.

Mark's on the trail of some long dead monks

and the cunning trap they left behind.

Even in the drizzle, Poppit Sands in Wales is a popular beach.

A great place to sit back and take in the view.

But sometimes we can't see what's under our noses.

We all like to look out to see,

and we know the history of the sea,

but there's often hidden histories

underneath the sea.

For hundreds of years,

these waters were hiding an Atlantis-like structure,

best seen from up high when the tide is low.

A few years ago this remarkable picture was taken.

We're standing just there, but here is this extraordinary

v-shaped feature,

which the archaeologists interpreted as a medieval fish trap,

capable of bagging literally thousands of fish.

The aerial view revealed a submerged stone structure -

a man-made pen to trap fish at low tide.

It's around 900 years old.

How did something so big become forgotten?

I'm here with local diver Ziggy Otto.

-Hi.

-Hello.

Why did it take so long for us archaeologists to find this?

I mean, it's so enormous.

Because it's covered, even at low tide,

because sea-level has risen, and I believe by,

and this is an estimate of,

a metre over the past thousand years,

so, once upon a time

this fish trap was inter tidal,

exposed at low tide.

How did it actually work?

You have a wide opening that was possibly even extended by nets

even further to corral the fish into the trap,

possible close the trap and let the tide go out and pick up your fish.

A very, very efficient system.

You'd come and pick up the fish who were thrashing around in the sand.

Absolutely.

This man-made rock pool is over 800 feet long,

painstakingly built from stones piled up by hand.

An extraordinary achievement

for the men who constructed it in the 12th century.

In its heyday, this trap would be capable

of catching thousands of fish,

but who was mad enough to spend the money

to build and maintain such a contraption?

A bird's eye view, once again, gives us a clue.

The long gardens, here at St Dogmaels,

are unusually narrow -

typical of the sort of plots farmed by medieval tenants,

whose landlords lived just next-door.

Those landlords were the original inhabitants of this,

St Dogmaels Abbey, founded from France around 1120,

and whose monks had to live on a diet of fish.

The abbey's original community consisted of 13 monks,

brought over from France by the Norman baron Robert fitz Martin.

As historian Glen Johnson knows, being members of a Benedictine order

their monastic rule banned red meat

meaning they needed a large amount of fish.

So, it was the only meat they could have as part of the diet.

How often they ate meat, we don't know,

but all of it would have been fish and the trap, then,

obviously, would have been very valuable

to making sure that they had a constant supply.

The industrious monks in their monastery

would have once dominated the landscape.

But the tides of time were turning against them.

It began with the black death, in 1349.

What had been a full house of honest and obedient monks were decimated

by the arrival of this disease, and the abbey, to be honest,

never really recovered.

In the end, it went the way of all flesh

with Henry VIII, a man who liked to chop and change.

In 1536, Henry VIII had ordered the dissolution of the monasteries.

When Henry's men had finished at St Dogmaels,

the abbey was ruined.

Then the monk's fish trap was lost

as the sea-level rose over the centuries.

But one ecclesiastical influence did survive the passage of time.

Seine fishing is now a Welsh tradition,

but historians believe it was first brought over

by the French monks from the River Seine.

So, Cyril, you've been fishing on this river for how long?

30 years.

And you've presumably caught

a fair few fish in those times.

Oh, yes, I've caught a few in my time, yes.

So, how does this process actually work?

Well, there's a boat and a crew of four -

the Captain and the three nets men.

As you pull the net in, you pull in slowly.

You can see it's like a little horseshoe

So, the whole thing runs like a bag?

Like a bag, yes. That's what it is.

That's what a Seine net is.

And you have to come in at low tide?

Yes, well if you're fishing, you're on high water, the tide is in,

you haven't got any beach to land the net, you know?

This will be ten ft of water around here.

You've got no room to stand.

So, now they're pulling the bottom of the net in,

and, yes, there's a fish in it.

Where?

There's a fish in the net.

Going through the net a mullet it is...

look it's still in the net

I can see it, yes there it is

That's a Sewin.

Only a few miles from our medieval trap,

but a thousand years later, tidal fishing lives on.

The times have changed but our reliance on our tides has not.

We're on a journey to work out the riddle of the tides,

the mysterious endless ebb and flow around our coast,

and the curious ways we've put it to use.

Canny Yorkshire folk saw a money making opportunity at Scarborough.

Some 300 years ago, the nation fell in love with sea-bathing,

a craze that began here.

But the town had to find a way of tempting refined gentlefolk

down to the water, even at low tide.

Tessa is here to discover

how Scarborough made sea-bathing fashionable

In the mid 1800s, the population here was booming.

Visitors flooded in,

and grand hotels were built to accommodate the crowds.

By the time Victoria was on the throne, we'd gone bathing-mad.

But for a town

that was selling itself

on a swim in the sea,

sometimes there was a bit of a problem.

Where is the sea?

Low tide reveals a huge expanse of beach

and takes the sea a long way out.

For a prim and proper Victorian lady, frolicking across the sand

in her undies to meet the sea was out of the question,

so, in Scarborough, they came up with this -

a modesty cabinet, a bathing machine

in which a woman could shelter

as she was wheeled out to meet the tide.

The very first evidence of a bathing machine in Britain

is this image from 1736, set right here in Scarborough.

And to get a glimpse of one of these contraptions

I'm meeting Karen Snowden from the Scarborough museum.

Hidden at the back of her storeroom,

there's a bathing machine that's survived,

but only just.

Here we are.

It's seen better days, hasn't it?

Yes, it has.

It spent many decades as a garden shed in Scarborough.

When does it date from, do you know?

Probably about 1870.

I think it's fair to say that this bathing machine is out of service.

So, just to see just how the bathing belles would have used them,

we're going to have to get a bit creative.

A bathing machine probably hasn't been built in Britain

for about 100 years,

but perhaps that's because nobody's tried, until now.

And here it is!

Basically, a DIY shed on wheels.

And, of course, we need an unflappable horse,

so, there's Brooklyn with her very own stable boy.

We also need a dipper,

a woman to help our lady dip into the sea.

Cue Karen from the museum.

And now all we need is the Victorian lady to take a dip.

That'll be me.

-Well, Carol, we've got this picture here of how it once was.

-Yeah.

How do you reckon we're looking?

Well, not bad. Quite a close match.

-It is, isn't it?

-Yeah.

Why did people want to dip in icy waters?

They thought it was good for their health, and the colder the better.

The idea isn't exactly filling me with joy but it's time to beach test

our 21st-century bathing machine.

C'mon. Walk on!

The ladies could get changed on the way to the sea

so that they were never seen in their indecent bathing costume.

As my dipper, what would you be doing, what's your main role?

I'd help you change and then I'd help you into the sea,

and if you were a little bit reluctant to go all the way under,

-I'd shove you under.

-Thanks for that, Karen.

I feel like I should be going to a cocktail party in this outfit,

not for a swim.

-Has the horse had enough?

-Yeah.

-I don't blame her. Do you?

-No.

So I'm not to swim, am I, cos I don't know how to swim?

No, you don't know how to swim. You just dunk.

Are we going to wait for a big wave?

Yeah, there's a couple of big ones coming up soon, let's go for them.

OK, push me.

SHE SCREAMS

-Oh, a nice big one coming.

-OK.

In their modesty, Victorian ladies bathed out of sight,

but by the early 20th century, the horses were pensioned off

as women became bolder about showing themselves.

At low tide, suddenly the beach was the place to be seen.

As sunbathing took hold, women no longer hid away.

Instead, they wanted costumes to show off their curves.

By the early 20th century, costumes started to look more familiar.

They were often hand-knitted with wool.

Stylish on the beach, but wool is soggy and shapeless when wet.

So a swimwear revolution was set to explode in the 1950s.

We'd fallen in love with the flimsy, figure-hugging nylon costume

like this.

-Nylon was the wonder of the new age.

-Beachwear has certainly changed

since the days when Victorian maidens tiptoed gingerly

down to the water's edge shrouded in thick wool.

Scientists could engineer swimwear that could withstand

the worst of the tide and still retain its shape.

Man-made fibres seemed like a miracle fit for both sunbathing

and swimming.

I want to understand exactly what nylon is.

How do you make a man-made fibre?

Chemist David Smith from the University of York

is going to show me how two unremarkable-looking chemicals

revolutionised the swimming costume.

Let's make nylon. What is it, first of all?

So, nylon is a giant molecule, really long molecules.

And what are these molecules made from?

Well, they're made from two reagents that we have here,

and they each have reactive groups, so they're going to react

and form long chains, a bit like if I held hands with somebody else

and somebody else and we built a long chain along the beach.

We're going to pour the one reagent on top of the other

and you've got to float it in down the side.

Right, a bit like pouring cream on coffee.

Exactly like that, yeah.

In between the layers, you should see a film forming between the two.

Yeah, yeah, I do, actually.

So do I just penetrate the film, David?

That's right, just to where the film is, and then agitate slightly,

and you'll be able to then pull the film out.

Oh, wow. Is that a bit of nylon?

That's a bit of nylon that we've got there.

So, what it shows, really, is that you can take two chemicals,

mix them together and make a fabric.

You don't have to wait for the sheep or for the cotton to grow.

You can do it with chemicals.

And is nylon itself waterproof?

It dries very fast and the water doesn't penetrate very well,

so certainly compared to what was around before nylon,

it was a big step forward, especially for swimwear.

By reinventing swimwear over the ages,

we have coped with the changing tides of beach fashion.

We wanted it all, a cossie for the sand and the surf.

Nylon certainly made a splash on the beach, but what's it like wet?

Looks like I can't escape one last dip.

I'm off to buy a wetsuit.

Timing the tide right for a dip makes life more convenient.

But for commerce, it's vital.

All around our coast, businesses run to the rhythm of the sea,

especially the Port of Liverpool.

The mouth of the Mersey yawns wide open into the Irish Sea.

As the tide rushes in, the estuary swallows a vast deluge of water.

The flood brings in seafood for the wildlife of the marshes.

The tide also carries in cargo ships - big ones.

They do a dangerous dance over sandbanks

that can only be cleared at high water.

It's a race against the tide twice a day.

No wonder Liverpool has always kept a close eye on the tides.

They've been measuring the rise and the fall of the sea here

for over 250 years. It's the longest tidal record in the UK.

Sailors watched the water so closely

to try and work out what it's going to do next.

Ray, as a Mersey skipper, do you carry tide tables on your boat?

I do, yes, it's here right now, it's like a Bible.

We have one of them all the time.

-This is your Bible?

-It certainly is.

Time and tide wait for no man.

But mariners did have to wait an awfully long time

to get truly accurate tide tables.

The riddle of the tides turns out to be

much, much harder to crack than you'd think.

There's more to predicting tides than the pull of the moon.

You've got to add in the gravity of the sun,

account for multiple elliptical orbits,

the tilt of the earth. The complexity goes on.

What about the depth of the sea, the shape of the coast?

Over centuries, the best brains solved pieces of the puzzle,

but before computers, tidal maths was too complex

to be worked out in your head.

So, calculating machines had to be invented.

In the 1940s, all that effort to solve the riddle of the tides

finally reached its high water mark here in Liverpool

with the construction of a mechanical brain.

The cogs and wheels of tide-predicting machines

used to whirr away inside Bidston Observatory,

on a hill overlooking the mighty Mersey.

This site was once the nerve centre for global tide tables.

Most of the British Empire ports

relied on the calculations done at Bidston.

But now the machines that crunched the numbers

are a bit crunched themselves.

Deep in storage at National Museums Liverpool,

the tidal prediction machines are in bits.

Now, for the first time in years, one of the mechanical brains

is about to be re-assembled.

Wow, look at that.

Lots of brass, cast iron, steel axles,

absolutely stunning, isn't it?

-At the time, this was state of the art.

-It was indeed, yes.

When these wheels rotated, they could forecast the future,

the future of the sea.

But how?

While the original machine is carefully pieced back together,

I'm heading to the museum on Liverpool's quayside,

where Alan Bowden has something to show me.

So this is a model of a tide prediction machine.

It's absolutely beautiful, but what are the main principles

driving the computations, the predictions that it's making?

It's actually quite a complex set of mathematical equations

which depend on a number of variables,

and on this little model we've only selected four variables.

For instance, we've got the impact of the moon,

which is the principal component on the earth's tides,

we've got the impact of the sun,

and then we have two other variables here, for instance,

we have the eccentricity of the moon's orbit,

and then on this one here we have the effect of the sun -

it's higher in summer, lower in winter.

Adjustments must also be made to take account of local variations

like the shape of the coast.

So this wire is the processor, this is the thing that amalgamates

the readings from different variables and converts them to a line...

And converts them to a line which gives us high tide

and the low tide and the points in between.

The full-scale machine had 42 variables

and took one and a half days

to run a year of tide predictions for one port.

Liverpool became the world centre for tidal prediction

thanks to one man - Arthur Doodson.

He devoted his life to improving

and perfecting tidal prediction machines at Bidston Observatory.

But Arthur also needed workers to operate them -

people he called computers.

So you worked in the basement?

We did. One of the machines was down here.

Arthur Doodson's daughter-in-law

worked on the wheels of tidal fortune here for 44 years.

Valerie Doodson retired from Bidston, but now she's back.

-Wow. Is this it?

-This is where it all happened for the years

that we operated the Doodson-Lege tide predicting machine.

It was situated in this room facing this wall,

but with a space behind it,

cos we needed to get at the back to set it up.

Well, that's an example of setting up the machine.

One person set it up and another person checked the information.

And who are these people?

These are the tidal computers

in the early part of the 1960s, and that's me, but don't tell anyone.

Oh, wow! Wonderful.

These girls probably are 16. 16 or 17.

It has been said that he likes to surround himself

with attractive young women.

Well, I didn't like to say anything, but...

So there we go.

Very young to be doing such a difficult, responsible job.

So what's this card here, Valerie?

This is the setting card for Penang.

But that's in Malaya?

That's correct, yes. For 1965,

and it's predicting the high and low water.

The cards are very neatly filled in, aren't they?

Very important.

One test we had when we came for interview was a handwriting test.

If your handwriting didn't meet the requirement,

you didn't get the job.

I have subsequently been called a perfectionist,

because mistakes were not tolerated.

During its heyday, Bidston prepared tide tables

for ports across the British Empire.

Their work was crucial during the Second World War.

The Atlantic Wall has been penetrated.

Indeed, the computers even predicted low tide for the D-Day landings,

where avoiding submerged Nazi sea defences was vital to success.

Now we have a solid foothold on Fortress Europa,

men and materiel are poured onto the newly-won beachheads

with every favourable tide.

By the late 1960s, new electronic computers had taken over.

The role of the mechanical machines and their operators

has largely been forgotten.

But now, after years of hibernation,

the machine that predicted tides in the Second World War is reborn.

This is absolutely wonderful.

It's a little bit more exciting than looking at a modern circuit board.

Looking back from an age in which calculations are conducted

invisibly from within modern computer software,

this incredible piece of mechanical hardware is a reminder

that maths is beautiful, it's elegant,

that it decodes universal mysteries.

Without maths and without this very ingenious machine,

we couldn't have solved the riddle of the tides.

Ingenuity feeds the industry of Liverpool.

The docks were built to trap precious seawater behind their gates,

because at low tide, the water rushes away from the city.

Nearby, that leaves Antony Gormley's Iron Men

gazing wistfully after the retreating seas.

Twice a day, the shallow sloping beaches of the north-west coast

look more like a desert.

When the sea shrinks away from Southport Pier,

it becomes a walkway over the sand.

Just a few miles further north at the resourceful resort of Blackpool,

they've constructed their own ingenious contraption

to harness the power of the town's big tides.

DISCORDANT ORGAN NOTES

The sweet music of the sea.

It might not be very tuneful, but this is the tide talking

through the pipes of a rather remarkable organ.

My name's Liam Curtin,

and with my friend John Gooding, we built the Blackpool High Tide Organ.

Down on the beach, the tide is still out. It's on its way in.

We can have a look at what powers the organ.

So here is one of the ductile iron pipes attached to the sea wall.

That feeds the organ at high tide, sea comes in, swells and falls,

and as it swells, pushes air up there and into the organ.

There's eight of these fanned out along the promenade.

All organs need a source of air. In this case we're using the sea,

but other organs might use bellows,

something to push the air into the pipes,

and to demonstrate this, we can go and look at a very famous organ.

Well, here it is, the mighty Wurlitzer.

HE PLAYS THE WURLITZER

The bellows in this organ have replaced the sea in our organ,

pushing air into the pipes in the same sort of way.

That makes the bellows swell, so it makes it louder,

and there's doors that can close to muffle pipes

and a whole range of effects.

You can play any tune on it, unlike the Blackpool High Tide Organ,

which is more of an ambient thing,

just responding to the chaos of the weather.

The weather's got a bit worse,

but in a way that's better for the organ,

because there's a bit of swell and we can hear its chords now,

and along with it we've got James Lancaster, a musician,

who's come to play along with it.

TRUMPET AND TIDAL ORGAN PLAY

The tidal organ sits in screaming distance

of Blackpool's more energetic attractions.

The sea comes in and out, as the punters are shaken all about!

The donkeys retreat as the water rises.

For some, the daily ebb and flow up and down the beach

is bad for business.

But for others, it's a big draw.

Further south, the power of the tide alone pulls people out to Jersey.

The Channel Islands are one of our great natural wonders.

Sitting on the edge of the Atlantic Ocean,

they have an exceptionally high rise and fall of water.

The heaving of the sea reveals secret caves...

..before the tide closes them shut again.

That ebb and flow makes this a magical, shape-shifting coast.

At low water on Jersey,

a submerged undersea world is exposed just offshore.

Especially when there's a spring tide.

That's when the moon and the sun line up.

Their combined gravitational pull causes an extra-strong tidal effect.

A natural performance Miranda can't resist.

A spring tide is a fascinating time to explore the coast.

Not only does the water come up really high,

but more interestingly for me, it goes out really low,

revealing wildlife that's usually hidden beneath the waves.

The effect of the spring tide on Jersey is spectacular.

So much of the seabed here lies just below water level

that at low spring tide,

parts of the island expand over two miles outwards.

It leaves this old coastal fort high and dry,

and this is where I'm heading.

The Seymour Tower will be my base

to explore an extraordinary landscape of temporary rock pools,

teeming with wildlife.

These miniature water worlds only exist for a few short hours.

With the sea gone, I've got to get a move on.

In no time this vast lunar landscape is going to be submerged again,

and we've just got a very brief window

to get out to the Seymour Tower and set up camp.

And then tomorrow we can really explore the Atlantic

surging in and out around us.

-Hi!

-Bob, how are you doing?

-Very well!

Bob Tompkins is my guide.

He grew up on Jersey and knows every nook and cranny

of this short-lived landscape.

So what's the time window that we've got to get out there?

Roughly three quarters of an hour to be on the safe side.

I mean, the sands here are shifting all the time, all the time.

The tide operates in a pincer movement here.

It comes up through the gully on that side,

but it's sweeping around the curve of the reef here

and coming up through the beach this way as well.

The sea can easily surround the unwary.

Dashing for the slippery steps of this rescue tower

to sit out the tide could save your life.

Look at that! That is majestic, isn't it?

Yeah.

Can't believe we're finally here.

-It seemed such a long way back there, and here we are.

-Yeah.

-My castle awaits.

-Yep.

Wow! Look at this. This is really special, isn't it?

-Home from home. Get the fire going.

-Wood-burning stove.

-Yeah.

From this Napoleonic fortress, I can explore the marine life

the Atlantic is about to bring to my doorstep.

The jeep beats a rapid retreat, but I'm staying.

The ocean soon rushes in around me,

transforming the tower into an island.

Tomorrow, I'll explore the sea life stranded on the seabed around me,

as the Atlantic rushes out again.

The next morning it's me that's still stranded way offshore,

waiting for the tide to turn.

When it does, I'll be well-placed to scramble.

I'm hoping as the water floods away

that it's left some interesting wildlife

trapped in the pools behind me.

These mega rock pools won't be around for long.

I have a 20-minute window to swim

and see what the Atlantic has brought in.

This has to be the weirdest thing I've ever done in a rock pool.

I held out my hand and I felt something tickling on it,

and it's actually a little brown shrimp,

who normally hide away in little holes.

They're actually coming up and sitting on my hand,

and I think they're actually feeding off little bits of skin.

This is very bizarre.

It's amazing how quickly the water drains away.

The rock pools shrink with every minute,

leaving wildlife looking for cover.

Well, surely the find of the day, this is a brown crab.

A male brown crab.

They don't find females around here for some reason.

By the looks of things he's just shed his carapace.

It's not quite hard, so he's probably come in here,

where it's relatively protected.

He can shed and have a few days to recover and harden up the next shell

and then he'll be off out. Handsome chap.

The water's rushing away from me fast,

so now I can explore the very edge of the low spring tide on foot.

The tide's gone out pretty far now,

but it's left these little pools of water,

and with rock pooling, every rock tells a story.

You need to pick them all up and have a good look at them.

This one looks good, I'll just turn that one over.

You can see this beautiful snakelocks anemone there.

You only ever find those actually in the water,

they can't retract their tentacles like a beadlet anemone does.

So those need to live in water.

But this is interesting, there's this orange encrusting sponge,

and you can see that it's formed a line there.

That line will tell me where the low water mark is.

That sponge needs to grow in water,

and it won't grow any higher up that line.

Let's put that back carefully, make sure everything's under water.

Ordinarily, I'd have no place being here.

I'm walking two miles offshore on what's normally the seabed.

Here the sea life have to adopt strategies to survive.

This cloud of green is actually thousands of tiny worms,

known locally as mint sauce worms,

who shrink into the sand at the sign of a predator.

Over time, this spider crab shell has been camouflaged by seaweed,

and banded dog whelks don't go anywhere without their armour.

Creatures thrive in the rich soup of nutrients

the tide conveniently washes their way twice a day.

Farmers also make the most of the Atlantic's bounty

to fatten up millions of rock oysters.

Out on the edge is a really special place to be.

Much of this environment is under water for most of the time,

and it's only at these really, really low spring tides

that you can get out here.

So much more than just rocks and seaweed.

This place is teeming with life.

But with the spring tide now on the turn,

I have a bit of a trek to make it all the way back to dry land.

Where the sea has room to breathe,

the water can disappear well offshore.

But where the tide is trapped, beware.

The Isle of Anglesey sits snugly next to mainland Wales.

Between them lies the Menai Strait,

a straitjacket for the surging tide.

With nowhere else to go,

the water must speed up to make it through the rocky channel.

Fast-flowing water floods the strait with food

that makes this the ideal location for fattening up mussels.

Sea farmers collect their mussels in specially designed boats,

which do a merry dance to harvest their crop.

Whatever their craft,

all around the Anglesey coast, sailors respect the raging tide.

Even the bigger boats seek shelter.

They hide behind sturdy sea walls.

But I'm not hiding.

For me, the final riddle of the tides is how to tame them.

I'm about to take on the great surge of the Atlantic tide

as it squeezes around the ferocious rocks and reefs just off Anglesey.

And I'm going to be in a boat not much bigger than a matchstick.

Nigel Dennis was one of the first men to kayak right around Britain.

He knows the waters here are amongst the most challenging we have.

The tide creates powerful surges in the sea.

The water races on, carrying kayaks with it for fun.

These tidal races are a test of both skill and stomach.

Now it's my turn.

I'm a beginner, Nigel.

OK, this already looks moderately serious to me.

You're going to be stretched a little bit today.

So how much paddling have we done?

Well, I've done quite a lot of what I call canoeing

-on inland waters and rivers.

-Kayaking, kayaking, this is.

This is something very different, isn't it?

This is kayaking, this is for the ocean.

And have you done anything in tides, moving water?

I've done a little bit, Nigel, a little bit.

But I can tell this is way beyond anything I've experienced before.

Right, OK. So the tide's going to be pushing us towards the rocks,

towards the race, and we're going to drop down through the water.

And what's the chance of me turning a kayak upside-down and capsizing?

Today, 50/50.

-That's pretty high odds!

-The first bit is easy.

-I'll have to do some practicing!

-The first bit is easy!

-Yes, yes!

-OK, I'll give you a hand with your boat.

-OK.

So, Nigel, in this little moment of calm, well, it's not really calm,

all these things are relative for me,

but can you just tell me what tides mean to a kayaker, a sea kayaker?

Well, it's really important that kayakers understand what it means.

You can go around the corner on a calm day and end up in a tide race,

and people won't have the skill, or the power,

to get out of the flowing water,

so they'll actually be sucked straight through the race.

So you need skills, power, but also a deep knowledge of how tides work?

I mean, we call it seamanship, really.

Some people have a natural understanding

and other people never learn.

THEY LAUGH

And just when I'm thinking I've got the hang of it,

the tide trips me up.

OK. Just give us your boat, just hop back in...

Just plonk yourself back in.

Good! Well done.

How did you did get to the flat water and then capsize?

HE LAUGHS

Lack of concentration.

The rocky outcrops don't just produce swirling waters.

They also create a curious feeling of claustrophobia,

which adds to my anxiety.

Caught between two emotions, fear and exhilaration.

Are we going into the tide or with it, are we going with the tide?

Yes, the first tiny bit of tide, you can just see it up ahead.

You call it a tiny bit of tide but I can see white horses...

The first heart in mouth moment.

A tide race off one of the most dangerous coasts in Britain.

It's kind of exciting. A real thrill.

But I'm sweating buckets trying not to turn upside down.

These waves are so big that in the troughs I can see nothing but sea.

We're working with the tide, not fighting against it,

and I can really feel its full force pushing me onwards.

Just keep paddling, you're doing really well.

Nice and relaxed, that's good!

My battle against the tide was a one-off.

I'm just happy to have made it through in one piece.

But all around our coast, every minute of every day,

the tides rule the rhythm of people's lives.

I've just discovered how tricky tides can be.

After capsizing and an awful lot of paddling,

I'm back on the beach taking in one of nature's great free shows,

the ebb and flow of this vast body of water,

whose restless motion is driven by the heavens.

It's awe-inspiring.

Subtitles by Red Bee Media Ltd