0:00:04 > 0:00:07Coast is home.
0:00:09 > 0:00:14We're back to explore the most endlessly fascinating shoreline
0:00:14 > 0:00:16in the world - our own!
0:00:18 > 0:00:23The quest to discover surprising, secret stories
0:00:23 > 0:00:25from around the British Isles continues.
0:00:30 > 0:00:33This is Coast.
0:01:03 > 0:01:05For as long as we've gazed
0:01:05 > 0:01:07from our island shores over the seas,
0:01:07 > 0:01:10we've struggled to solve
0:01:10 > 0:01:12the mystery of our tides.
0:01:12 > 0:01:17Twice a day, like the chest of a sleeping giant,
0:01:17 > 0:01:19the sea heaves up and down,
0:01:19 > 0:01:21re-drawing the shape of our island home.
0:01:21 > 0:01:26The effect of the two tides varies around the coast.
0:01:26 > 0:01:27In the Bristol Channel,
0:01:27 > 0:01:32we have one of the greatest surges of water in the world.
0:01:32 > 0:01:35It creates the remarkable Severn Bore.
0:01:35 > 0:01:39Over in East Anglia in the south-east corner of England,
0:01:39 > 0:01:42the tides are relatively weak.
0:01:42 > 0:01:45Down here on the south coast, the opposite is true,
0:01:45 > 0:01:48because the tides get forced up and down the English Channel
0:01:48 > 0:01:53around a promontory called Portland Bill.
0:01:53 > 0:01:56You get huge standing waves there. It's really scary.
0:01:59 > 0:02:02Why does the sea behave so differently around our coast?
0:02:02 > 0:02:07We're here to explore The Riddle Of The Tides.
0:02:09 > 0:02:13My tidal odyssey takes me to the North West,
0:02:13 > 0:02:16and a city that sits by the sea.
0:02:16 > 0:02:20In Liverpool, I'm on the trail of a forgotten genius,
0:02:20 > 0:02:23who made a machine to calculate the tides anywhere, any time.
0:02:26 > 0:02:31Look at that, lots of brass, cast iron, steel axles,
0:02:31 > 0:02:33absolutely stunning, isn't it?
0:02:35 > 0:02:41But my journey begins on tidal rapids. The Menai Strait...
0:02:44 > 0:02:47..a narrow ribbon of wild water.
0:02:53 > 0:02:58Mariners have always been at the mercy of the tides.
0:02:58 > 0:03:01Trying to master those turbulent waters
0:03:01 > 0:03:04was a great voyage of discovery.
0:03:07 > 0:03:13I'm setting sail on this 19th-century-style schooner...
0:03:13 > 0:03:15Shall we put it up, Scott?
0:03:15 > 0:03:16Yes, go for it.
0:03:16 > 0:03:21..to see how salty seadogs began to tackle the riddle of the tides.
0:03:21 > 0:03:24Good work-out, isn't it?
0:03:24 > 0:03:27It's all hands on deck as we rush to set sail
0:03:27 > 0:03:30before the tide turns against us.
0:03:30 > 0:03:32Proper old ropes that takes the skin off your hands.
0:03:39 > 0:03:44A tricky passage awaits along some of Britain's most treacherous waters.
0:03:44 > 0:03:47Navigating the Menai Strait isn't for the faint-hearted.
0:03:47 > 0:03:51We're racing to make it through The Swellies -
0:03:51 > 0:03:55the tidal surge around the island of Anglesey.
0:03:55 > 0:03:59Any misjudgement of the tides here could wreck the boat on jagged rocks.
0:03:59 > 0:04:03It's a real worry for the skipper, Scott Metcalfe.
0:04:03 > 0:04:06Quite a few people have come to grief.
0:04:06 > 0:04:09There's a lot of rocks around here, there's rocks on this side,
0:04:09 > 0:04:11and certainly there's rocks on the other side,
0:04:11 > 0:04:14the Cribbin Rock, which is quite a nasty one.
0:04:14 > 0:04:15If you get the timing wrong
0:04:15 > 0:04:16you can get swept onto
0:04:16 > 0:04:18one of the rocks, basically.
0:04:18 > 0:04:20And this is a, you know, a historic vessel.
0:04:20 > 0:04:25How important were tides back in the days before motors?
0:04:25 > 0:04:27Very, very important.
0:04:27 > 0:04:29I don't know if you can see those two white posts,
0:04:29 > 0:04:32we should have those basically in line.
0:04:32 > 0:04:34So, you line the two white posts up,
0:04:34 > 0:04:38steer for the posts, and that gets you through the deeper channel.
0:04:38 > 0:04:40People talk about The Swellies
0:04:40 > 0:04:42as if it's some kind of white-knuckle fairground ride.
0:04:42 > 0:04:43What are The Swellies?
0:04:43 > 0:04:47That's just this stretch of water between the two bridges, basically.
0:04:47 > 0:04:52It is the fastest flowing part. This is the most treacherous part.
0:04:52 > 0:04:57Scott makes sure to navigate The Swellies at slack water -
0:04:57 > 0:05:02the brief period when the tidal flow is weakest.
0:05:02 > 0:05:07For sailors, reading the mood of the sea is a matter of life and death.
0:05:08 > 0:05:10Since the earliest times,
0:05:10 > 0:05:13mariners have known that the moon drives the tides,
0:05:13 > 0:05:16but how, exactly?
0:05:16 > 0:05:19And why are there two tides a day?
0:05:19 > 0:05:25Sailing with me is Tom Rippeth from Bangor University.
0:05:25 > 0:05:26Tom, can you explain to me
0:05:26 > 0:05:29why it is that we get two tides every 24 hours?
0:05:29 > 0:05:31We've got a simple model, here, Nick.
0:05:31 > 0:05:32If you'd just like to hold that.
0:05:32 > 0:05:34Yes.
0:05:34 > 0:05:35This is obviously the Earth,
0:05:35 > 0:05:36and then here we have the moon
0:05:36 > 0:05:39and, erm, the Earth and moon,
0:05:39 > 0:05:42basically, orbit around each other in space,
0:05:42 > 0:05:44and there's two forces acting, really.
0:05:44 > 0:05:47There's one force which is the moon's gravitational pull,
0:05:47 > 0:05:50and another force which is the centrifugal force,
0:05:50 > 0:05:54which is pulling the water away from the planet.
0:05:54 > 0:05:58The Earth's motion and the moon's gravity make the tides.
0:05:58 > 0:06:03To see how, imagine our planet completely covered in water.
0:06:03 > 0:06:07One bulge in the sea is caused by the moon's pull.
0:06:07 > 0:06:12There's an opposite bulge because water gets pushed out
0:06:12 > 0:06:15by centrifugal force, as the Earth whizzes through space.
0:06:17 > 0:06:22The Earth also rotates, once every 24 hours.
0:06:24 > 0:06:28Measure the sea level at a single point
0:06:28 > 0:06:33and it rises as the Earth spins, and then falls again,
0:06:33 > 0:06:41and sea level rises again 12 hours later, so two high tides a day.
0:06:41 > 0:06:44But our world isn't completely submerged,
0:06:44 > 0:06:47the shape of the coastline and cliffs on the sea bed,
0:06:47 > 0:06:49like the Continental Shelf,
0:06:49 > 0:06:54disrupt the flow of water, changing the height of our tides.
0:06:54 > 0:06:57Our tides go up and down at the edge of the Continental Shelf,
0:06:57 > 0:07:00and that generates tidal waves.
0:07:00 > 0:07:02So, we're not talking about a gradual rising
0:07:02 > 0:07:05and falling of water every, what, six hours, roughly?
0:07:05 > 0:07:07Absolutely not. We're talking about waves
0:07:07 > 0:07:11which will travel down one coastline and travel up another coastline,
0:07:11 > 0:07:14so, for instance, down the east coast of England,
0:07:14 > 0:07:16we'll see big changes in the height of the tide,
0:07:16 > 0:07:19but also in the timing of the tide,
0:07:19 > 0:07:21so you might have low water in the north,
0:07:21 > 0:07:23and you might have high water in the south.
0:07:23 > 0:07:25So, our tides aren't simple.
0:07:25 > 0:07:28They travel in massive waves,
0:07:28 > 0:07:32which makes it hard to predict the sea-level.
0:07:32 > 0:07:36Tom's wave tank shows how the tide behaves differently,
0:07:36 > 0:07:38depending where you are.
0:07:38 > 0:07:41Here we've just put three examples on the Irish Sea.
0:07:41 > 0:07:45We've got Liverpool, here, which has very large tides,
0:07:45 > 0:07:48and if you move elsewhere in the Irish sea, we actually see
0:07:48 > 0:07:49places where it's high water at Liverpool
0:07:49 > 0:07:51and it can be low water elsewhere.
0:07:51 > 0:07:54So, you can have high water at different times
0:07:54 > 0:07:56- in different parts of the coast? - That's right.
0:07:56 > 0:07:59- It's a very complex system, isn't it? - Absolutely, very complex.
0:07:59 > 0:08:04Tides are further complicated by our craggy shoreline,
0:08:04 > 0:08:08which makes predicting them very tricky.
0:08:08 > 0:08:12But later I'll discover a remarkable machine,
0:08:12 > 0:08:15created to crack the puzzle.
0:08:17 > 0:08:21All around our coast, businesses run to the rhythm of the sea,
0:08:21 > 0:08:25especially the Port of Liverpool.
0:08:28 > 0:08:32The mouth of the Mersey yawns wide open into the Irish Sea.
0:08:32 > 0:08:39As the tide rushes in, the estuary swallows a vast deluge of water.
0:08:39 > 0:08:44The flood brings in seafood for the wildlife of the marshes.
0:08:44 > 0:08:51The tide also carries in cargo ships - big ones.
0:08:51 > 0:08:55They do a dangerous dance over sandbanks
0:08:55 > 0:08:58that can only be cleared at high water.
0:08:59 > 0:09:04It's a race against the tide twice a day.
0:09:10 > 0:09:14No wonder Liverpool has always kept a close eye on the tides.
0:09:14 > 0:09:18They've been measuring the rise and the fall of the sea here
0:09:18 > 0:09:24for over 250 years. It's the longest tidal record in the UK.
0:09:24 > 0:09:27Sailors watched the water so closely
0:09:27 > 0:09:31to try and work out what it's going to do next.
0:09:31 > 0:09:34Ray, as a Mersey skipper, do you carry tide tables on your boat?
0:09:34 > 0:09:37I do, yes, it's here right now, it's like a Bible.
0:09:37 > 0:09:39We have one of them all the time.
0:09:39 > 0:09:41- This is your Bible?- It certainly is.
0:09:41 > 0:09:43Time and tide wait for no man.
0:09:43 > 0:09:46But mariners did have to wait an awfully long time
0:09:46 > 0:09:49to get truly accurate tide tables.
0:09:54 > 0:09:57The riddle of the tides turns out to be
0:09:57 > 0:09:59much, much harder to crack than you'd think.
0:09:59 > 0:10:04There's more to predicting tides than the pull of the moon.
0:10:04 > 0:10:07You've got to add in the gravity of the sun,
0:10:07 > 0:10:10account for multiple elliptical orbits,
0:10:10 > 0:10:13the tilt of the Earth. The complexity goes on.
0:10:13 > 0:10:17What about the depth of the sea, the shape of the coast?
0:10:17 > 0:10:21Over centuries, the best brains solved pieces of the puzzle,
0:10:21 > 0:10:24but before computers, tidal maths was too complex
0:10:24 > 0:10:27to be worked out in your head.
0:10:27 > 0:10:30So, calculating machines had to be invented.
0:10:30 > 0:10:35In the 1940s, all that effort to solve the riddle of the tides
0:10:35 > 0:10:39finally reached its high water mark here in Liverpool
0:10:39 > 0:10:42with the construction of a mechanical brain.
0:10:42 > 0:10:46The cogs and wheels of tide-predicting machines
0:10:46 > 0:10:50used to whirr away inside Bidston Observatory,
0:10:50 > 0:10:53on a hill overlooking the mighty Mersey.
0:10:54 > 0:10:58This site was once the nerve centre for global tide tables.
0:10:58 > 0:11:01Most of the British Empire ports
0:11:01 > 0:11:05relied on the calculations done at Bidston.
0:11:05 > 0:11:09But now the machines that crunched the numbers
0:11:09 > 0:11:11are a bit crunched themselves.
0:11:13 > 0:11:17Deep in storage at National Museums Liverpool,
0:11:17 > 0:11:20the tidal prediction machines are in bits.
0:11:22 > 0:11:26Now, for the first time in years, one of the mechanical brains
0:11:26 > 0:11:28is about to be re-assembled.
0:11:30 > 0:11:32Wow, look at that.
0:11:34 > 0:11:38Lots of brass, cast iron, steel axles,
0:11:38 > 0:11:42absolutely stunning, isn't it?
0:11:42 > 0:11:45- At the time, this was state of the art.- It was indeed, yes.
0:11:45 > 0:11:49When these wheels rotated, they could forecast the future,
0:11:49 > 0:11:53the future of the sea.
0:11:53 > 0:11:55But how?
0:11:55 > 0:12:00While the original machine is carefully pieced back together,
0:12:00 > 0:12:03I'm heading to the museum on Liverpool's quayside,
0:12:03 > 0:12:05where Alan Bowden has something to show me.
0:12:08 > 0:12:10So this is a model of a tide prediction machine.
0:12:10 > 0:12:14It's absolutely beautiful, but what are the main principles
0:12:14 > 0:12:17driving the computations, the predictions that it's making?
0:12:17 > 0:12:21It's actually quite a complex set of mathematical equations
0:12:21 > 0:12:23which depend on a number of variables,
0:12:23 > 0:12:26and on this little model we've only selected four variables.
0:12:26 > 0:12:30For instance, we've got the impact of the moon,
0:12:30 > 0:12:33which is the principal component on the earth's tides,
0:12:33 > 0:12:35we've got the impact of the sun,
0:12:35 > 0:12:38and then we have two other variables here, for instance,
0:12:38 > 0:12:41we have the eccentricity of the moon's orbit,
0:12:41 > 0:12:45and then on this one here we have the effect of the sun -
0:12:45 > 0:12:48it's higher in summer, lower in winter.
0:12:48 > 0:12:53Adjustments must also be made to take account of local variations,
0:12:53 > 0:12:57like the shape of the coast.
0:12:57 > 0:13:01So this wire is the processor, this is the thing that amalgamates
0:13:01 > 0:13:04the readings from different variables and converts them to a line...
0:13:04 > 0:13:09And converts them to a line which gives us high tide
0:13:09 > 0:13:11and the low tide and the points in between.
0:13:11 > 0:13:16The full-scale machine had 42 variables
0:13:16 > 0:13:18and took one and a half days
0:13:18 > 0:13:22to run a year of tide predictions for one port.
0:13:22 > 0:13:27Liverpool became the world centre for tidal prediction
0:13:27 > 0:13:31thanks to one man - Arthur Doodson.
0:13:31 > 0:13:33He devoted his life to improving
0:13:33 > 0:13:36and perfecting tidal prediction machines at Bidston Observatory.
0:13:38 > 0:13:40But Arthur also needed workers to operate them -
0:13:40 > 0:13:43people he called computers.
0:13:45 > 0:13:47So you worked in the basement?
0:13:47 > 0:13:49We did. One of the machines was down here.
0:13:49 > 0:13:52Arthur Doodson's daughter-in-law
0:13:52 > 0:13:57worked on the wheels of tidal fortune here for 44 years.
0:13:57 > 0:14:01Valerie Doodson retired from Bidston, but now she's back.
0:14:02 > 0:14:07- Wow. Is this it?- This is where it all happened for the years
0:14:07 > 0:14:11that we operated the Doodson-Lege tide predicting machine.
0:14:11 > 0:14:15It was situated in this room facing this wall,
0:14:15 > 0:14:17but with a space behind it,
0:14:17 > 0:14:19cos we needed to get at the back to set it up.
0:14:19 > 0:14:22Well, that's an example of setting up the machine.
0:14:22 > 0:14:27One person set it up and another person checked the information.
0:14:27 > 0:14:29And who are these people?
0:14:29 > 0:14:31These are the tidal computers
0:14:31 > 0:14:37in the early part of the 1960s, and that's me, but don't tell anyone.
0:14:37 > 0:14:41Oh, wow! Wonderful.
0:14:41 > 0:14:42So what's this card here, Valerie?
0:14:42 > 0:14:45This is the setting card for Penang.
0:14:45 > 0:14:47But that's in Malaya?
0:14:47 > 0:14:52That's correct, yes. For 1965,
0:14:52 > 0:14:54and it's predicting the high and low water.
0:14:54 > 0:14:57The cards are very neatly filled in, aren't they?
0:14:57 > 0:14:58Very important.
0:14:58 > 0:15:02One test we had when we came for interview was a handwriting test.
0:15:02 > 0:15:04If your handwriting didn't meet the requirement,
0:15:04 > 0:15:05you didn't get the job.
0:15:05 > 0:15:08I have subsequently been called a perfectionist,
0:15:08 > 0:15:10because mistakes were not tolerated.
0:15:12 > 0:15:16During its heyday, Bidston prepared tide tables
0:15:16 > 0:15:18for ports across the British Empire.
0:15:18 > 0:15:22Their work was crucial during the Second World War.
0:15:23 > 0:15:27The Atlantic Wall has been penetrated.
0:15:27 > 0:15:31Indeed, the computers even predicted low tide for the D-Day landings,
0:15:31 > 0:15:37where avoiding submerged Nazi sea defences was vital to success.
0:15:37 > 0:15:40Now we have a solid foothold on Fortress Europa,
0:15:40 > 0:15:43men and material are poured onto the newly-won beachheads
0:15:43 > 0:15:44with every favourable tide.
0:15:45 > 0:15:50By the late 1960s, new electronic computers had taken over.
0:15:52 > 0:15:56The role of the mechanical machines and their operators
0:15:56 > 0:15:57has largely been forgotten.
0:15:59 > 0:16:02But now, after years of hibernation,
0:16:02 > 0:16:07the machine that predicted tides in the Second World War is reborn.
0:16:21 > 0:16:23This is absolutely wonderful.
0:16:23 > 0:16:27It's a little bit more exciting than looking at a modern circuit board.
0:16:31 > 0:16:34Looking back from an age in which calculations are conducted
0:16:34 > 0:16:36invisibly from within modern computer software,
0:16:36 > 0:16:41this incredible piece of mechanical hardware is a reminder
0:16:41 > 0:16:43that maths is beautiful, it's elegant,
0:16:43 > 0:16:46that it decodes universal mysteries.
0:16:46 > 0:16:50Without maths and without this very ingenious machine,
0:16:50 > 0:16:55we couldn't have solved the riddle of the tides.
0:17:02 > 0:17:06Ingenuity feeds the industry of Liverpool.
0:17:06 > 0:17:10The docks were built to trap precious seawater behind their gates,
0:17:10 > 0:17:13because at low tide, the water rushes away from the city.
0:17:16 > 0:17:19Nearby, that leaves Antony Gormley's Iron Men
0:17:19 > 0:17:23gazing wistfully after the retreating seas.
0:17:28 > 0:17:33The Isle of Anglesey sits snugly next to mainland Wales.
0:17:33 > 0:17:36Between them lies the Menai Strait,
0:17:36 > 0:17:41a straitjacket for the surging tide.
0:17:41 > 0:17:43With nowhere else to go,
0:17:43 > 0:17:46the water must speed up to make it through the rocky channel.
0:17:48 > 0:17:52Fast-flowing water floods the strait with food
0:17:52 > 0:17:57that makes this the ideal location for fattening up mussels.
0:17:57 > 0:18:02Sea farmers collect their mussels in specially designed boats,
0:18:02 > 0:18:06which do a merry dance to harvest their crop.
0:18:09 > 0:18:11Whatever their craft,
0:18:11 > 0:18:16all around the Anglesey coast, sailors respect the raging tide.
0:18:16 > 0:18:19Even the bigger boats seek shelter.
0:18:19 > 0:18:22They hide behind sturdy sea walls.
0:18:23 > 0:18:26But I'm not hiding.
0:18:26 > 0:18:31For me, the final riddle of the tides is how to tame them.
0:18:32 > 0:18:37I'm about to take on the great surge of the Atlantic tide
0:18:37 > 0:18:42as it squeezes around the ferocious rocks and reefs just off Anglesey.
0:18:42 > 0:18:45And I'm going to be in a boat not much bigger than a matchstick.
0:18:47 > 0:18:53Nigel Dennis was one of the first men to kayak right around Britain.
0:18:53 > 0:18:57He knows the waters here are amongst the most challenging we have.
0:18:57 > 0:19:01The tide creates powerful surges in the sea.
0:19:01 > 0:19:05The water races on, carrying kayaks with it for fun.
0:19:05 > 0:19:10These tidal races are a test of both skill and stomach.
0:19:10 > 0:19:13Now it's my turn.
0:19:13 > 0:19:15I'm a beginner, Nigel.
0:19:15 > 0:19:19OK, this already looks moderately serious to me.
0:19:19 > 0:19:22You're going to be stretched a little bit today.
0:19:22 > 0:19:24So how much paddling have we done?
0:19:24 > 0:19:27Well, I've done quite a lot of what I call canoeing
0:19:27 > 0:19:29- on inland waters and rivers. - Kayaking, kayaking, this is.
0:19:29 > 0:19:32This is something very different, isn't it?
0:19:32 > 0:19:34This is kayaking, this is for the ocean.
0:19:34 > 0:19:37And have you done anything in tides, moving water?
0:19:37 > 0:19:39I've done a little bit, Nigel, a little bit.
0:19:39 > 0:19:42But I can tell this is way beyond anything I've experienced before.
0:19:42 > 0:19:47Right, OK. So the tide's going to be pushing us towards the rocks,
0:19:47 > 0:19:52towards the race, and we're going to drop down through the water.
0:19:52 > 0:19:55- OK, I'll give you a hand with your boat.- OK.
0:20:03 > 0:20:08So, Nigel, in this little moment of calm, well, it's not really calm,
0:20:08 > 0:20:10all these things are relative for me,
0:20:10 > 0:20:15but can you just tell me what tides mean to a kayaker, a sea kayaker?
0:20:16 > 0:20:23Well, it's really important that kayakers understand what it means.
0:20:23 > 0:20:28You can go around the corner on a calm day and end up in a tide race,
0:20:28 > 0:20:31and people won't have the skill, or the power,
0:20:31 > 0:20:33to get out of the flowing water,
0:20:33 > 0:20:36so they'll actually be sucked straight through the race.
0:20:36 > 0:20:42So you need skills, power, but also a deep knowledge of how tides work?
0:20:42 > 0:20:44I mean, we call it seamanship, really.
0:20:44 > 0:20:46Some people have a natural understanding
0:20:46 > 0:20:49and other people never learn.
0:20:49 > 0:20:51THEY LAUGH
0:20:53 > 0:20:57And just when I'm thinking I've got the hang of it,
0:20:57 > 0:20:59the tide trips me up.
0:21:11 > 0:21:15OK. Just give us your boat, just hop back in...
0:21:17 > 0:21:19Just plonk yourself back in.
0:21:21 > 0:21:22Good! Well done.
0:21:24 > 0:21:27How did you get to the flat water and then capsize?
0:21:27 > 0:21:29HE LAUGHS
0:21:29 > 0:21:31Lack of concentration.
0:21:33 > 0:21:37The rocky outcrops don't just produce swirling waters.
0:21:37 > 0:21:41They also create a curious feeling of claustrophobia,
0:21:41 > 0:21:44which adds to my anxiety.
0:21:46 > 0:21:49Caught between two emotions, fear and exhilaration.
0:21:50 > 0:21:54Are we going into the tide or with it, are we going with the tide?
0:21:54 > 0:21:57Yes, the first tiny bit of tide, you can just see it up ahead.
0:21:57 > 0:22:01You call it a tiny bit of tide but I can see white horses...
0:22:01 > 0:22:04The first heart in mouth moment.
0:22:04 > 0:22:09A tide race off one of the most dangerous coasts in Britain.
0:22:22 > 0:22:26It's kind of exciting. A real thrill.
0:22:26 > 0:22:29But I'm sweating buckets trying not to turn upside down.
0:22:29 > 0:22:34These waves are so big that in the troughs I can see nothing but sea.
0:22:45 > 0:22:48We're working with the tide, not fighting against it,
0:22:48 > 0:22:52and I can really feel its full force pushing me onwards.
0:22:57 > 0:23:01Just keep paddling, you're doing really well.
0:23:01 > 0:23:05Nice and relaxed, that's good!
0:23:05 > 0:23:08My battle against the tide was a one-off.
0:23:08 > 0:23:12I'm just happy to have made it through in one piece.
0:23:12 > 0:23:15But all around our coast, every minute of every day,
0:23:15 > 0:23:18the tides rule the rhythm of people's lives.
0:23:20 > 0:23:25I've just discovered how tricky tides can be.
0:23:25 > 0:23:28After capsizing and an awful lot of paddling,
0:23:28 > 0:23:34I'm back on the beach taking in one of nature's great free shows,
0:23:34 > 0:23:37the ebb and flow of this vast body of water,
0:23:37 > 0:23:44whose restless motion is driven by the heavens.
0:23:44 > 0:23:46It's awe-inspiring.
0:24:14 > 0:24:17Subtitles by Red Bee Media Ltd