Waves & Tides Fierce Earth


Waves & Tides

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On today's Fierce Earth, it's all about the awesome power of the sea.

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Here, in Santa Cruz, California, home of monster waves.

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And we have monsters here in the UK - monster tides.

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We'll find out how the sea goes from this...

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..To this. It's incredible!

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It's wet suits on for the Fierce Earth team, as we hit the surf

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to unlock the secrets of king-sized waves.

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Leah experiences one of the world's fastest rising tides.

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It's starting to get a little bit scary, actually.

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Remember to stay calm.

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I meet the awesome power of a rip current head on.

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-Good job, Leo, keep it up!

-I'm exhausted...

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And Captain Dougal rides the tides to guide a massive ship into port.

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That's one incredible sight to see.

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What happens when the ground shakes,

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the seas rise up and the air tears itself apart?

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The Fierce Earth team move in,

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taking on the most powerful forces on the planet.

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Get ready for Fierce Earth -

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the Earth, and how to survive it.

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The world's shorelines are in a never-ending battle with the sea.

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Battered by the huge force of the waves,

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year in year out, 24 hours a day.

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In the UK, the storms of Christmas 2013

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changed the shape of the coast for ever.

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Around the planet more than 3 billion people live by the sea.

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Waves can be dangerous and even cost lives,

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but when the sea is safe, they can be a lot of fun.

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We're here in Santa Cruz, California,

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home to some of the most famous coastline in the world.

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As you can see, it's pretty popular with surfers -

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that's because the waves here can be absolutely massive.

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We're here to find out why.

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People come from all over the world to ride these waves,

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which can be up to 15 metres tall -

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that's as high as a five-storey building.

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This place is paradise for thrill-seekers -

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making this beach one of the best surfing locations in the world.

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To understand how waves bring the sea to life,

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we first need to know what one is, and how it moves.

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OK, let it go on the ground...

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Whenever we think of waves, we think of the sea,

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but, in fact, waves are all around us.

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I can create my own with this skipping rope. Watch.

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Notice when Leo flicks his wrist,

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the energy transfers along the rope in the form of a wave.

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And that's exactly what happens when waves move through the sea.

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Waves are energy passing through water,

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and sometimes travelling for thousands of miles.

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The next piece of land in that direction is Japan,

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more than 5,000 miles away.

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Some of these waves have travelled almost that far.

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That distance is important in creating the huge waves

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that crash against this coast.

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If you look out there,

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you can just see Clare bobbing up and down on a boat.

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Hi, Clare!

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Hi, Leo! Although it looks like the water itself

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is moving towards Leo on the shore,

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a wave is actually ENERGY passing through the water.

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You can see the boat bobbing up and down

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as the energy of the wave passes underneath it,

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then make its way to shore where it breaks.

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OK, Clare, you can come in!

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So, where does this energy come from?

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Remember the skipping rope?

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Leo started that wave with a flick of his wrist.

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Well, out at sea, waves start with wind.

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Imagine this swimming pool is the Pacific Ocean.

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We're going to use a leaf blower to create a storm with high winds.

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Now, let's send Leo over to the other side of the ocean.

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OK, Clare, I'm in California.

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Now it's the fun part.

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I'm going to start a mini storm and send it in Leo's direction.

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You can see how rough the seas are,

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but as the waves move away from the storm,

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they become organised lines moving across the ocean

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towards the shoreline.

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You can see the energy from the storm

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that Clare has created over there

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has transferred across the pool in the form of these waves.

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So, it's wind that fuels waves.

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When a storm whips up out in the ocean,

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the longer and harder it blows,

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the more energy it propels towards the shore.

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A wave's long journey finally ends near the coast when it breaks,

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but this can only happen

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when the final piece of the jigsaw falls into place.

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As the ocean gets shallower near to the shore,

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the wave slows down due to the friction of the sea bed.

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As the water begins to mound up,

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the wave takes on its distinctive shape.

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Once it gets too tall, it breaks and rolls up the beach.

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At Santa Cruz, California, all these ingredients come together perfectly.

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Thousands of miles of ocean to build up all that energy,

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and then the perfect sea bed

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to create monster breakers like these.

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It's no wonder one sport has made its home here.

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Surfing.

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Leo and I are here to have a go, and we've got two very special teachers.

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Sam, 12, and Ben, 15, have lived next to the ocean all their lives.

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They've been surfing since they were five and are now Junior Champions.

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They're pretty good.

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Their challenge today is to get Clare and I doing this...

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..Well, maybe.

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-I'm Leo.

-Ben.

-Nice to meet you, Ben.

-Sam.

-Hi, Sam, how you doing?

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-So, you're going to teach us how to surf?

-Yeah, it should be fun.

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-So, do you guys surf every day?

-Yeah.

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And what makes it so fun

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that you can surf on the coldest day in winter?

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You just get good waves

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and it gets you happy when you do good turns.

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By following the surf forecasts online,

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the boys know in advance what the sea conditions are going to be like.

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But sometimes this sea gets dangerous,

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and that's where years of experience come in.

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It's important to understand where to be,

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so you don't get caught in a dangerous situation.

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And also you just never want to turn your back to the ocean

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because you'll never know if, like, a big wave is going to take you out.

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-Trying to read the waves.

-Your board doesn't want to be

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between you and the wave or, like, it's going to hit you.

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Today, the sea is fairly calm, but the waves off this coast

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are capable of smashing boats and surfboards in two

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with their awesome force.

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There's no way you'd get me out in a sea like that!

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If you want to harness the energy of a wave on a surfboard,

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you have to paddle yourself up to speed

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and leap from a lying position to standing up.

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Sam and Ben make it look very easy.

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Something tells me it isn't...

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So, if you're laying down on the board like this...paddling...

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whatever foot you put forward...

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I don't think I could even do that.

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Let's have a go.

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I don't think we're going to be the next World Champions!

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Too far forward, your nose is going to dig into the water

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-and you'll face-plant.

-Woo-hoo! Going to be fun!

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You're getting there, but you're going to need a lot of practice

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-before you get in the ocean.

-'I think he may be right.'

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OK, nice one.

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But, somehow, we persuade them to let us loose in the ocean.

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We head off to a beginners' beach where the boys learned to surf.

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Conditions are perfect, waves of about 1.5 metres.

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Easy for Sam and Ben,

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but they look like skyscrapers to us as we paddle out.

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After a few failed attempts to catch a wave, we're going nowhere.

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But, eventually, with a friendly shove from Ben,

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I get up on the wave.

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Sort of..

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The energy pushes me hundreds of metres into the shore,

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it's an amazing feeling.

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Now, it's Leo's turn, and he has to go one better and stand up.

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Show off!

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-Nice job.

-You guys were amazing.

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Without you two I just wouldn't have even got in the water.

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Yeah, you did really good. That one, you got in it.

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Sam, you're amazing! 12-year-old kid teaching me how to surf.

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-You rock!

-Got it first time!

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I can't believe the immense power of those waves.

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It was just incredible.

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And to think that thing travelled all the way across the ocean

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and just for that split second, you get to ride that force.

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-It's amazing, isn't it?

-It's better than that paddling!

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I want to go and get another one!

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-High-five!

-High-fives back!

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Still to come, Leo sees if he has what it takes to beat

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the ocean's hidden menace - the rip current.

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Feels like I'm going nowhere!

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Oceans cover 71% of the Earth's surface

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and contain 97% of the planet's water.

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The energy carried by waves means lots of fun for surfers

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and, as we now know, waves don't actually move the water.

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Think about the last time you went to the seaside.

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Throughout the day, the water level changes

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causing the beach to shrink and grow.

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This is the tide coming in and out.

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6,000 miles away from Santa Cruz in California is the UK,

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a place where tides are a very big deal.

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We're in South Wales.

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Behind us is the Severn Estuary,

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the mouth of Britain's longest river.

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The harbour here at the moment is completely full of water.

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But if we were just to wait another six hours,

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the sea level's going to drop an incredible 12 metres.

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To this. It's incredible.

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All of this variation in sea level is due to tides.

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And we're here to find out how they work.

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Tides are one of the great forces on our planet.

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Every day, most coastlines

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experience two high tides and two low tides.

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The driving force behind this constant change is gravity.

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What's going to happen if I throw this ball into the sky?

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Is it going to stay there, is it going to go upwards?

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No, we know what's going to happen.

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It's going to fall to the ground.

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That's because it's being pulled by a force called gravity

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drawing us all into the centre of the Earth.

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It keeps me standing here, it's dropped the ball to the ground

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and it also keeps the oceans in place.

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But we also know the oceans don't stay exactly where they are.

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They are constantly on the move,

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coming in and going out with the motion of the tides.

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Now, why is that?

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If you imagine this is the Earth with its own gravitational force,

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there's something missing here

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and that's up there in the sky.

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The moon.

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The moon travels round the Earth in one month

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and the moon, as a planet, has its own gravitational force

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but it's much weaker than that of the bigger Earth,

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but it's still strong enough to affect the oceans.

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As the moon moves around the Earth throughout each month,

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it pulls the oceans slightly towards it, helping to cause the tides.

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But there's another thing to think about.

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Imagine this is us on the Earth.

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The Earth is constantly spinning,

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giving us one day and one night every 24 hours.

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So, every 24 hours the Earth moves twice

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through the deep water giving us high tides,

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and twice through the shallow water giving us low tides.

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The difference between the height of a high tide

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and a low tide is called a tidal range.

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Almost nowhere in the world sees a bigger tidal range

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than here in the Severn Estuary.

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That's because of its distinctive funnel shape.

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If you've got Wales here and England there,

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the tide is being forced up this funnel-shape river mouth, like so.

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There's only one thing going to happen.

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The water mass is moving in and in as the tide rises,

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but it's getting funnelled in and there's land either side -

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it can't go anywhere,

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so it builds up, just like this sand here,

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and builds up and builds up and builds up.

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So, around about this part of the estuary,

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that's where you get the highest tides,

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because it's being forced into this funnel shape.

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This massive tidal range can be used to great effect by ports,

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because it means, at high tide,

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you can get enormous ships in and out of docks,

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like this one in Bristol.

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But you don't have long to do it.

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Every day, thousands of tonnes of cargo

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come in and out of this massive dock.

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They can bring anything from cars,

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coal, even toys, to Britain.

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But getting the huge ships that carry all of this

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in and out of the docks is a real assault course because of the tides.

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By measuring the distance of the moon from the Earth

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and understanding the shape of the sea bed,

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scientists can predict for many years ahead

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when we will have high and low tides.

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This channel controls the shipping in and out of the dock.

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Now, the level of water in the dock always stays high

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because of these giant gates, they lock the water back.

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But at low tide, we've got a problem.

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Look at the other side here.

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You can see the water level's down to less than a metre,

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you can see mud banks over there.

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There's no way we're going to get a large ship into the docks

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when the tide is low.

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There's only one way to do that -

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wait until the tide has risen high enough

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and very carefully guide the ship in.

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I'm here to meet Jerry.

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-Hello!

-Nice to see you. Welcome aboard.

-Great!

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He's like an air-traffic controller for ships.

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His job is to get as many ships into port as possible

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during the small window of opportunity.

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He needs to know exactly when the tide will be high

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and when it will be low.

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Harbour control...

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We're heading out into the estuary to meet a huge car container

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that's come all the way from Spain.

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She's quite a big ship, so she's probably about 35-40,000 tonnes.

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Big ship, 160-odd metres long.

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-You're not going to sail that through here?!

-Oh, yes!

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We have to drop nearly ten metres in the lock -

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that's the same as a three-storey building -

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to get to the same water level as out in the estuary.

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But once we're out there,

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it's obvious that the tide is rising rapidly.

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Wow, the estuary really is alive.

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You can see the water just rushing its way up the river.

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Look at the buoy over there, it's being bent towards inland.

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That's indicating that thousands and thousands of tonnes of water

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are working their way now directly up towards the port.

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The estuary is filling up at an amazing three metres per hour

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and, right on cue, our ship comes around the headland.

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SHIP FOGHORN BLOWS

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Dougal, there she is. That's your first sight of her.

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There she blows!

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But getting her into dock won't be easy.

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The fast-moving water heading up the estuary

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is trying to push the ship past the entrance to the port.

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This is the really critical moment.

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And this chunk of metal is being safely guided through

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-that very small gap, essentially using the tides.

-That's right.

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Without the tidal range we have here, she would not get in there.

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One more ship has safely run the assault course

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of a fast-rising tide.

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But it's not just boats who have to battle the tides in this estuary.

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People regularly get caught out, too.

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Like here at Sully Island, which lies 200m off the South Wales coast.

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At low tide, it's possible to walk over to it.

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But in the last five years,

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more than 50 people have been cut off by the lightning-quick tides,

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keeping the local RNLI team, like Nicola, very busy.

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What we're stood on here is the causeway

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and this is the area that gets cut off by the tide.

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When the tide comes in, it covers this area so you couldn't cross.

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In just a couple of hours' time

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there will be six metres of water above us,

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so a very, very dangerous area.

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Nicola wants to show me exactly how quick the water arrives

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and why YOU should never ignore warnings about tides.

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'I think I'm going to get my feet wet,

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'so she's kindly kitted me out in a warm dry suit.'

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-Wow, it is surrounding us quite quickly, isn't it?

-It is.

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-How much time do we have?

-About ten minutes before we're covered here.

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The plan is to see how long I can keep my footing

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as the water rushes to fill the channel

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between the island and the mainland.

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The guys are on standby.

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So, bring on the tide!

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I've got a highly-trained lifeboat crew watching me,

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so this is definitely not something you should ever try.

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I've only been here a couple of minutes,

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and I can't believe how fast the water's already surrounding me.

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I'm really glad I've got my wellies on. Look at this!

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This is incredible! This water is rushing up the channel so quickly

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that the sea level is rising by 20cm every five minutes.

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I'm experiencing one of the world's fastest tides.

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It's getting deeper,

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bashing against my legs and you've got the wind to contend with, too.

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I'm keeping calm, because I've got the safety guys on hand.

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Five minutes in, and I'm struggling to keep my footing

0:20:080:20:12

on the slippy rocks. The water's almost at the top of my legs.

0:20:120:20:16

It's starting to get a little bit scary, actually.

0:20:170:20:20

OK, this is all becoming a bit of a struggle,

0:20:200:20:23

so it's time for the guys to come and get me out.

0:20:230:20:26

I'm ready!

0:20:270:20:28

'It's a big relief to be pulled to safety.'

0:20:360:20:40

Thanks, guys!

0:20:400:20:42

Whoa! Whoa, whoa, whoa!

0:20:420:20:43

'It was very scary being cut off like that.

0:20:430:20:47

'If you go to the beach, remember to make sure an adult knows

0:20:470:20:50

'when the tides are coming in.'

0:20:500:20:52

I really wasn't expecting it to be that powerful.

0:20:560:20:59

A few minutes ago, it was trickling around my feet,

0:20:590:21:02

and then, before you know it,

0:21:020:21:03

two, three minutes later, it's up to your waist

0:21:030:21:06

and it's choppy and it's powerful and you've got the wind.

0:21:060:21:09

Without these guys, I would've been in a lot of trouble.

0:21:120:21:15

The work done by life-savers like the RNLI

0:21:200:21:23

keeps people out of harm's way at the seaside.

0:21:230:21:25

It's no different back in California,

0:21:270:21:29

where staying safe in the ocean is priority number one.

0:21:290:21:33

The hundreds of lifeguards who work here

0:21:350:21:38

are trained to be the best in the business.

0:21:380:21:41

Today's the annual try-out for Santa Cruz lifeguards.

0:21:410:21:45

These guys have to prove their swimming

0:21:450:21:47

and life-saving skills are up to the job.

0:21:470:21:50

That's because out in these oceans,

0:21:500:21:51

there's a hidden menace known as rip currents,

0:21:510:21:54

strong currents that pull people out to sea

0:21:540:21:56

responsible for 80% of all the US lifeguards' rescues.

0:21:560:21:59

Part of the team here is Gigi.

0:22:010:22:04

She's been patrolling these beaches for eight years,

0:22:040:22:07

so knows exactly how to spot a lurking rip current.

0:22:070:22:10

She's taking me to a notorious beach,

0:22:120:22:15

where swimmers and surfers face their threat every day.

0:22:150:22:18

My job as a lifeguard is to be constantly looking to see

0:22:210:22:24

if rip currents are being formed,

0:22:240:22:26

because that is one of the number-one rescues on the beach.

0:22:260:22:28

Rip currents can form on any sandy beach.

0:22:280:22:32

Powerful waves pound the shoreline...

0:22:330:22:36

..they break, releasing huge amounts of energy

0:22:400:22:43

but then all that water wants to flood back out to sea.

0:22:430:22:46

Sometimes a narrow channel forms in the sandy sea bed,

0:22:490:22:52

and this is the route that the water uses

0:22:520:22:54

to surge back out to sea in a rip current.

0:22:540:22:57

So a fast-moving current is actually flowing AWAY from the beach.

0:22:570:23:01

And when a swimmer gets caught in one,

0:23:030:23:05

they won't realise it until they look back at the beach

0:23:050:23:07

and see how far they've travelled out to sea.

0:23:070:23:10

It doesn't necessarily suck you under,

0:23:100:23:12

-it more sucks you straight out.

-And that can be pretty dangerous?

0:23:120:23:15

It can be extremely dangerous,

0:23:150:23:17

and all your energy will force you to get tired

0:23:170:23:20

and that's how a lot of drownings are caused.

0:23:200:23:22

It all sounds pretty scary.

0:23:230:23:25

But for my extreme challenge today, Gigi's got a plan to show me

0:23:250:23:29

how helpless it feels to be trapped in a powerful rip current.

0:23:290:23:32

It's too dangerous to swim in one for real,

0:23:360:23:39

but out here in the bay,

0:23:390:23:40

the conditions are perfect for our experiment.

0:23:400:23:43

Well, what we're going to do is put your bungee cord

0:23:450:23:48

around your waist and while the boat drifts,

0:23:480:23:51

you'll be pulling, as if you're being pulled in the current.

0:23:510:23:54

My challenge is to swim the 200 metres to shore,

0:23:560:23:58

that's eight lengths of an ordinary swimming pool,

0:23:580:24:01

with an elastic cord tying me to our boat.

0:24:010:24:04

The extra energy I'll need to tow the boat behind me

0:24:060:24:08

is going to feel just like swimming against a rip current.

0:24:080:24:12

It's going to be very, very tough.

0:24:120:24:14

And I hate cold water.

0:24:140:24:16

OK, I'm going in, Gigi.

0:24:240:24:26

-All right, Leo, you can do it.

-Oh, looks cold!

0:24:260:24:29

-Remember to stay calm.

-Ahh, it's freezing!

-Don't panic!

-Oohhh!

0:24:290:24:32

Although the sea is calm, this is a dangerous swim.

0:24:350:24:38

Pulling the weight of the boat behind me

0:24:380:24:40

is going to tire me out very quickly,

0:24:400:24:42

so Gigi will be my own personal lifeguard

0:24:420:24:44

alongside on her rescue board.

0:24:440:24:46

I make a good start.

0:24:560:24:57

Normally, I could swim 200 metres fairly easily,

0:24:580:25:01

but as the elastic extends,

0:25:010:25:02

I start to feel the pull of the boat behind me.

0:25:020:25:05

Feels like I'm going nowhere!

0:25:100:25:12

'I'm starting to tire and lose my technique,

0:25:130:25:16

'just like being in a real rip current.'

0:25:160:25:19

Keep going, Leo, you're doing good!

0:25:210:25:23

The best way to escape if this was real

0:25:240:25:26

would be to swim at right angles to the shore, like this...

0:25:260:25:30

But I don't have that choice today.

0:25:300:25:32

After just one and a half minutes,

0:25:350:25:36

I've only travelled 20 metres but I'm exhausted.

0:25:360:25:40

Fighting against the bungee has sapped all my energy.

0:25:410:25:44

So, Gigi comes to the rescue.

0:25:470:25:50

I feel like a drowned rat...!

0:25:570:25:58

If that had been a real rip,

0:26:030:26:05

I'd never have made it back to the shore.

0:26:050:26:07

Thank goodness Gigi was here.

0:26:070:26:10

These things are dangerous.

0:26:100:26:12

He did good. He gave a good effort, he tried hard.

0:26:120:26:15

It just goes to show that swimming straight into shore

0:26:150:26:18

is not an easy way to exit a rip current.

0:26:180:26:21

This was always going to be a tough challenge.

0:26:230:26:25

I've only managed to swim 20 metres,

0:26:250:26:28

a fraction of the distance to shore.

0:26:280:26:30

Fighting against a rip current is a battle you're not going to win.

0:26:300:26:34

The Fierce Earth team have been up close

0:26:390:26:41

with the living, breathing ocean.

0:26:410:26:43

The power of waves can be fun,

0:26:450:26:47

but you must never turn your back on them.

0:26:470:26:50

Always be aware of hidden rip currents.

0:26:510:26:54

Tides creep up and down under the pull of gravity.

0:26:560:26:59

Their power can helps ships into port,

0:26:590:27:02

but if you don't stay alert, their rapid rise can catch you out.

0:27:020:27:06

It's getting deeper, bashing against my legs.

0:27:070:27:10

Where the land meets the sea...

0:27:100:27:12

..we've learned the Earth can get very fierce.

0:27:140:27:17

In the very special next episode of Fierce Earth...

0:27:200:27:23

Leo chooses his most extreme moments ever.

0:27:230:27:26

Plus, an all-new exclusive challenge.

0:27:260:27:29

I'm going to take to the skies and fly like a bird.

0:27:290:27:32

He's saving the fiercest till last.

0:27:320:27:34

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