(Cry of seagulls)
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 lsles 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.
ln the Bristol Channel, we have one of the greatest surges of water in the world.
lt creates the remarkable Severn Bore.
Over in East Anglia, in the southeast 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. lt'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 Northwest, and a city that sits by the sea.
ln Liverpool, l'm on the trail of a forgotten genius
who made a machine to calculate the tides anywhere, any time.
Look at that.
Lots of brass, cast iron, steel axles.
Absolutely stunning, isn't it?
ln 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 rock pooling in Jersey.
This has to be the weirdest thing l've ever done in a rock pool.
That's actually 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.
- l don't blame her, do you? - No.
But my journey begins on tidal rapids -
the Menai Strait...
..a narrow ribbon of wild water.
Lower... Lower away on the forecastle.
Mariners have always been at the mercy of the tides.
Trying to master those turbulent waters was a great voyage of discovery.
..to see how salty seadogs began to tackle the riddle of the tides.
Good work-out, isn't it, earning a living?
lt's all hands on deck as we rush to set sail before the tide turns against us.
Proper old ropes that take the skin off your hands.
A tricky passage awaits along some of Britain's most treacherous waters.
Navigating the Menai Strait isn't for the faint-hearted.
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.
lt's a real worry for the skipper Scott Metcalfe.
SCOTT: 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.
lf you get the timing wrong, you can get swept onto one of the rocks, basically.
And this is a, you know, historic vessel.
How important were tides back in the days before motors?
Very, very important.
l don't know if you can see the 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 deep 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.
lt 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.
This is obviously the Earth, and then here we have the Moon,
and...
the Earth and Moon basically orbit round each other in space,
and 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 1 2 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 up another,
so for instance, down the east coast of England
you'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 lrish Sea.
We've got Liverpool here which has very large tides.
lf we move elsewhere in the lrish Sea, we 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?
- lt'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 l'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 lsle of Wight into the Solent
creates four high tides each day, double the normal number-
a challenge if you're messing about 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.
MAYA: This morning l've got to get my daughter Niaomh to school.
Did you brush your teeth?
Most parents have to check traffic reports in the morning, but for me, l check the tide tables.
MAYA: The tide controls my life here.
Unfortunately this morning, l've got to take Niaomh by van,
but this evening, hopefully, l'll be able to pick her up by kayak on the high tides.
For Maya, as for most parents, the school run is a frantic rush.
- Sorry we're a bit late. - No, you're fine.
But she's also rushing for another reason - she's racing against the tide.
MAYA: l'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.
MAYA: l'm going to hop in, and hopefully find a spider crab.
Shallow water means Maya can reach the bottom with one gulp of air.
l'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 under there where she'll keep all her eggs,
but we don't want the females, we want the males with the nice big juicy claws.
Look at this. He's amazing!
This is 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.
MAYA: lt's time to go and collect Niaomh now.
lf she times it right, Maya can kayak in with the tide...
MAYA: The tide time changes every day...
..collect Niaomh from school...
MAYA: ..so the teachers are really flexible to the fact that sometimes l 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?
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.
lt 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.
MARK: 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 sea, 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.
lt's around 900 years old.
How did something so big become forgotten?
l'm here with local diver Ziggy Otto.
- Hi. - Hi, there.
Why did it take so long for us archaeologists to find this?
lt's so enormous.
Because it's covered, even at low tide, because sea level has risen,
l believe by, and this is an estimate,
a metre over the past 1 ,000 years,
so once upon a time, this fish trap was inter-tidal, exposed at low tide.
MARK: 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, possibly close the trap,
and let the tide go out and pick up your fish.
A very, very efficient system.
You'd come out and just 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 1 2th century.
ln its heyday, this trap would have been 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 sorts 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 1 1 20, and whose monks had to live on a diet of fish.
The abbey's original community consisted of 1 3 monks,
brought over from France by the Norman Baron Robert Fitzmartin.
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.
lt 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 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.
lt began with the Black Death.
ln 1 349, what had been a full house of honest and obedient monks
was decimated by the arrival of this disease,
and the abbey, to be honest, never really recovered.
ln the end it went the way of all flesh with Henry Vlll,
a man who liked to chop and change.
ln 1 536, Henry Vlll had ordered the dissolution of the monasteries.
When Henry's men had finished at St Dogmaels, the abbey was ruined.
Then the monks'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, l'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're pulling 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 does.
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.
This will be ten feet 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? - Fish in the net.
Going through the net. A mullet, it is.
- Look, it's still in the net. - l can see it. Yes, there it is!
That's a sewin.
Only a few miles from our medieval trap, but 1,000 years later, tidal fishing lives on.
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 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.
TESSA: ln the mid-1 800s, 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 1 736, set right here in Scarborough.
And to get a glimpse of one of these contraptions,
l'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.
lt's seen better days, hasn't it?
Yes, it has.
lt spent many decades as a garden shed in Scarborough.
When does it actually date from?
Probably about 1 870.
l think it's fair to say that this bathing machine is out of service.
So 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 1 00 years,
but perhaps that's because nobody's tried...
until now.
And here it is. Basically a DlY 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, Karen, we've got this picture here of how it once was.
How do you reckon we're looking?
- Not bad. Quite a close match. - lt is, isn't it?
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 21 st-century bathing machine.
Come on, 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?
l'd help you change, and then l'd help you into the sea,
and if you were a little bit reluctant to go all the way under, l'd shove you under.
Thanks for that, Karen.
l feel like l should be going to a cocktail party in this outfit, not for a swim.
Has the horse had enough?
- Yeah. - l don't blame her, do you?
No.
l'm not to swim, am l, cos l 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!
- Whoo! - We're almost there.
- Oh, a nice big one coming. - OK.
(Tessa gasps)
ln 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.
lnstead, 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 1 950s.
We'd fallen in love with the flimsy, figure-hugging nylon costume like this.
Nylon was the wonder of the new age.
BROADCASTER: Beachwear has 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.
l 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?
Nylon's a giant molecule, really long molecule.
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,
like if l held hands with somebody, 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 we've got to float it in down the side.
- Right, a bit like pouring cream on coffee? - Exactly like that, yeah.
ln between the layers you should see a film forming between the two.
Yeah, yeah, l do, actually.
So, do l just penetrate the film, David?
That's right, just to where the film is, and then agitate slightly.
You'll be able to then pull the film out.
- 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?
lt dries fast, and water doesn't penetrate very well,
so 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 cozzie for the sand and the surf.
Nylon certainly made a splash on the beach, but what's it like wet?
Looks like l can't escape one last dip.
l'm off to buy a wetsuit.
NlCK: 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 lrish 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.
lt'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.
lt's the longest tidal record in the UK.
Sailors watch 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?
l do, yes. lt's here right now. lt's like a Bible. We use one of them all the time.
- This is your Bible? - lt 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 tide 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.
ln the 1 940s, 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 whir 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.
Look at that!
Lots of brass, cast iron, steel axles.
Absolutely stunning, isn't it?
- At the time, this was state of the art. - lt 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,
l'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.
lt's absolutely beautiful, but what are the main principles driving the computations,
the predictions that it's making?
lt'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.
Then on this one here, we have the effect of the Sun that'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...
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 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, this is it.
This is where it all happened for the years that we operated the tide-predicting machine.
lt 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.
That's an example of setting up the machine.
One person set it up, and another person checked the information.
Who are these people?
These are the tidal computers...
in the early part of the 1 960s,
and that's me, but don't tell anyone.
Wow! Wonderful.
These girls are probably...1 6.
1 6 or 1 7.
lt has been said that he liked to surround himself with attractive young women.
Well, l didn't like to say anything, but...
So, there you go.
NlCK: Very young to be doing a difficult, responsible job.
So, what's this card here?
This is the setting card for Penang.
But that's in Malaya.
That's correct, yes.
For 1 965.
And it's predicting the high and low water.
The cards are very neatly filled in, aren't they?
Very important.
A test we had when we came for interview was a handwriting test,
and if your handwriting didn't meet the requirement, then you didn't get the job.
l 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.
BROADCASTER: The Atlantic Wall has been penetrated.
NlCK: lndeed, the computers even predicted low tide for the D-day landings,
where avoiding the submerged Nazi sea defences was vital to success.
BROADCASTER: Now they have a solid foothold on Fortress Europa,
men and material are poured onto the beachheads with every favourable tide.
NlCK: By the late 1 960s, 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. lt'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, it decodes universal mysteries.
Without maths, and without this very ingenious machine,
we couldn't have solved the riddle of the tides.
lngenuity 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 lron Men gazing wistfully after the retreating seas.
Twice a day, the shallow sloping beaches of the northwest 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.
(Music plays)
The sweet music of the sea.
lt might not be very tuneful,
but this is the tide talking through the pipes of a rather remarkable organ.
My name's Liam Curtin. With my friend John Gooding, l built the Blackpool High Tide Organ.
(Music continues to play)
Down on the beach...
the tide's still out.
lt'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.
The 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.
ln 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.
(Plays organ)
LlAM: The bellows in this organ have replaced the sea in our organ,
pushing air into the pipes in the same sort of way.
You can make the bellows swell so it makes it louder,
and there's, like, 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.
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 lslands 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 liesjust below water level
that at low spring tide, parts of the island expand over two miles outwards.
lt leaves this old coastal fort high and dry, and this is where l am heading.
The Seymour Tower will be my base to explore an extraordinary landscape
of temporary rock pools teaming with wildlife.
These miniature water worlds only exist for a few short hours.
With the sea gone, l've got to get a move on.
ln 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. - How are you doing?
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.
The sands here are shifting all the time, all the time.
The tide operates in a pincer movement here.
lt 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. lt seemed such a long way back there, and here we are.
- My castle awaits. - Yeah.
Wow, look at this. This is really special, isn't it?
Home from home.
- Get the fire going. - Wood-burning stove.
From this Napoleonic Fortress, l can explore the marine life
the Atlantic is about to bring to my doorstep.
The Jeep beats a rapid retreat but l'm staying.
The ocean soon rushes in around me, transforming the tower into an island.
Tomorrow l'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, l'll be well placed to scramble.
l'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.
l have a 20-minute window to swim, and see what the Atlantic has brought in.
Has to be the weirdest thing l've ever done in a rock pool.
l held out my hand, and l felt something tickling on it,
and it's little brown shrimp who are normally hiding away in little holes,
but they're actually coming up and sitting on my hand.
l think they're actually feeding off little bits of skin.
lt's very bizarre.
lt'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. You don't find females around here for some reason.
And 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,
and he can shed, and have a few days to recover, harden up the next shell,
and he'll be off out.
Handsome chap.
The water's rushing away from me fast,
so now l 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.
And this one looks good.
l'll just turn that one over.
You can see this beautiful snakelock anemone there,
and 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, and 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 underwater.
Ordinarily, l'd have no place being here.
l'm walking two miles offshore on what's normally the seabed.
Here, the sea life has 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 underwater for most of the time,
and its 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,
l have a bit of a trek to make it all the way back to dry land.
NlCK: Where the sea has room to breathe, the water can disappear well offshore.
But where the tide is trapped, beware.
The lsle 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 l'm not hiding. For me, the final riddle of the tides is how to tame them.
l'm about to take on the great surge of the Atlantic tide
as it squeezes around these ferocious rocks and reefs just off Anglesey,
and l'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.
l'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, l've done quite a lot of what l call canoeing on inland waters and rivers.
- Kayaking, this is. - This is something very different.
This is kayaking. This is for the ocean.
Have you done anything in tides, moving water?
l've done a little bit, a little bit, but already l can tell
this is way beyond anything l've experienced before.
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's easy. - l'll have to practise.
- The first bit's easy. - Yes, yes...
OK, l'll give you a hand with your boat.
So, Nigel, in this little moment of calm before... 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 just sucked straight through the race.
NlCK: So you need skills, power, but also a deep knowledge of how tides work.
We call it seamanship, really.
Some people have a natural understanding, and other people never learn.
(Both laugh)
And just when l'm thinking l've got the hang of it, the tide trips me up.
Whoa!
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?
(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? - We're going with the tide.
The first tiny bit of tide, you can just see it up ahead.
You call it a tiny bit of tide, but l can see white horses.
First heart-in-mouth moment.
A tide race off one of the most dangerous coasts in Britain.
Kind of exciting, a real thrill, but l'm sweating buckets trying not to turn upside-down.
These waves are so big that in the troughs l can see nothing but sea.
We're working with the tide, not fighting against it,
and l 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.
l'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.
l've just discovered how tricky tides can be.
After capsizing and an awful lot of paddling, l'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.
lt's awe-inspiring.