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On today's Fierce Earth, it's all about the awesome power of the sea. | 0:00:02 | 0:00:07 | |
Here, in Santa Cruz, California, home of monster waves. | 0:00:07 | 0:00:10 | |
And we have monsters here in the UK - monster tides. | 0:00:12 | 0:00:17 | |
We'll find out how the sea goes from this... | 0:00:17 | 0:00:20 | |
..To this. It's incredible! | 0:00:20 | 0:00:22 | |
It's wet suits on for the Fierce Earth team, as we hit the surf | 0:00:28 | 0:00:31 | |
to unlock the secrets of king-sized waves. | 0:00:31 | 0:00:34 | |
Leah experiences one of the world's fastest rising tides. | 0:00:39 | 0:00:43 | |
It's starting to get a little bit scary, actually. | 0:00:43 | 0:00:46 | |
Remember to stay calm. | 0:00:46 | 0:00:47 | |
I meet the awesome power of a rip current head on. | 0:00:47 | 0:00:51 | |
-Good job, Leo, keep it up! -I'm exhausted... | 0:00:52 | 0:00:55 | |
And Captain Dougal rides the tides to guide a massive ship into port. | 0:00:57 | 0:01:02 | |
That's one incredible sight to see. | 0:01:03 | 0:01:06 | |
What happens when the ground shakes, | 0:01:06 | 0:01:10 | |
the seas rise up and the air tears itself apart? | 0:01:10 | 0:01:14 | |
The Fierce Earth team move in, | 0:01:14 | 0:01:16 | |
taking on the most powerful forces on the planet. | 0:01:16 | 0:01:19 | |
Get ready for Fierce Earth - | 0:01:37 | 0:01:38 | |
the Earth, and how to survive it. | 0:01:38 | 0:01:40 | |
The world's shorelines are in a never-ending battle with the sea. | 0:01:43 | 0:01:47 | |
Battered by the huge force of the waves, | 0:01:47 | 0:01:49 | |
year in year out, 24 hours a day. | 0:01:49 | 0:01:52 | |
In the UK, the storms of Christmas 2013 | 0:01:53 | 0:01:56 | |
changed the shape of the coast for ever. | 0:01:56 | 0:01:59 | |
Around the planet more than 3 billion people live by the sea. | 0:01:59 | 0:02:02 | |
Waves can be dangerous and even cost lives, | 0:02:02 | 0:02:05 | |
but when the sea is safe, they can be a lot of fun. | 0:02:05 | 0:02:08 | |
We're here in Santa Cruz, California, | 0:02:08 | 0:02:10 | |
home to some of the most famous coastline in the world. | 0:02:10 | 0:02:13 | |
As you can see, it's pretty popular with surfers - | 0:02:13 | 0:02:15 | |
that's because the waves here can be absolutely massive. | 0:02:15 | 0:02:18 | |
We're here to find out why. | 0:02:18 | 0:02:20 | |
People come from all over the world to ride these waves, | 0:02:25 | 0:02:28 | |
which can be up to 15 metres tall - | 0:02:28 | 0:02:30 | |
that's as high as a five-storey building. | 0:02:30 | 0:02:33 | |
This place is paradise for thrill-seekers - | 0:02:35 | 0:02:38 | |
making this beach one of the best surfing locations in the world. | 0:02:38 | 0:02:43 | |
To understand how waves bring the sea to life, | 0:02:43 | 0:02:45 | |
we first need to know what one is, and how it moves. | 0:02:45 | 0:02:49 | |
OK, let it go on the ground... | 0:02:51 | 0:02:54 | |
Whenever we think of waves, we think of the sea, | 0:02:54 | 0:02:56 | |
but, in fact, waves are all around us. | 0:02:56 | 0:02:58 | |
I can create my own with this skipping rope. Watch. | 0:02:58 | 0:03:01 | |
Notice when Leo flicks his wrist, | 0:03:04 | 0:03:06 | |
the energy transfers along the rope in the form of a wave. | 0:03:06 | 0:03:09 | |
And that's exactly what happens when waves move through the sea. | 0:03:13 | 0:03:16 | |
Waves are energy passing through water, | 0:03:22 | 0:03:25 | |
and sometimes travelling for thousands of miles. | 0:03:25 | 0:03:28 | |
The next piece of land in that direction is Japan, | 0:03:31 | 0:03:33 | |
more than 5,000 miles away. | 0:03:33 | 0:03:35 | |
Some of these waves have travelled almost that far. | 0:03:35 | 0:03:38 | |
That distance is important in creating the huge waves | 0:03:38 | 0:03:40 | |
that crash against this coast. | 0:03:40 | 0:03:42 | |
If you look out there, | 0:03:42 | 0:03:43 | |
you can just see Clare bobbing up and down on a boat. | 0:03:43 | 0:03:47 | |
Hi, Clare! | 0:03:47 | 0:03:49 | |
Hi, Leo! Although it looks like the water itself | 0:03:49 | 0:03:51 | |
is moving towards Leo on the shore, | 0:03:51 | 0:03:53 | |
a wave is actually ENERGY passing through the water. | 0:03:53 | 0:03:58 | |
You can see the boat bobbing up and down | 0:03:58 | 0:04:00 | |
as the energy of the wave passes underneath it, | 0:04:00 | 0:04:03 | |
then make its way to shore where it breaks. | 0:04:03 | 0:04:05 | |
OK, Clare, you can come in! | 0:04:05 | 0:04:08 | |
So, where does this energy come from? | 0:04:10 | 0:04:13 | |
Remember the skipping rope? | 0:04:13 | 0:04:14 | |
Leo started that wave with a flick of his wrist. | 0:04:14 | 0:04:17 | |
Well, out at sea, waves start with wind. | 0:04:17 | 0:04:19 | |
Imagine this swimming pool is the Pacific Ocean. | 0:04:23 | 0:04:26 | |
We're going to use a leaf blower to create a storm with high winds. | 0:04:29 | 0:04:33 | |
Now, let's send Leo over to the other side of the ocean. | 0:04:35 | 0:04:38 | |
OK, Clare, I'm in California. | 0:04:39 | 0:04:42 | |
Now it's the fun part. | 0:04:43 | 0:04:44 | |
I'm going to start a mini storm and send it in Leo's direction. | 0:04:44 | 0:04:49 | |
You can see how rough the seas are, | 0:04:49 | 0:04:51 | |
but as the waves move away from the storm, | 0:04:51 | 0:04:54 | |
they become organised lines moving across the ocean | 0:04:54 | 0:04:57 | |
towards the shoreline. | 0:04:57 | 0:04:59 | |
You can see the energy from the storm | 0:04:59 | 0:05:01 | |
that Clare has created over there | 0:05:01 | 0:05:03 | |
has transferred across the pool in the form of these waves. | 0:05:03 | 0:05:06 | |
So, it's wind that fuels waves. | 0:05:07 | 0:05:10 | |
When a storm whips up out in the ocean, | 0:05:13 | 0:05:15 | |
the longer and harder it blows, | 0:05:15 | 0:05:17 | |
the more energy it propels towards the shore. | 0:05:17 | 0:05:20 | |
A wave's long journey finally ends near the coast when it breaks, | 0:05:21 | 0:05:25 | |
but this can only happen | 0:05:25 | 0:05:27 | |
when the final piece of the jigsaw falls into place. | 0:05:27 | 0:05:30 | |
As the ocean gets shallower near to the shore, | 0:05:33 | 0:05:35 | |
the wave slows down due to the friction of the sea bed. | 0:05:35 | 0:05:39 | |
As the water begins to mound up, | 0:05:40 | 0:05:42 | |
the wave takes on its distinctive shape. | 0:05:42 | 0:05:45 | |
Once it gets too tall, it breaks and rolls up the beach. | 0:05:45 | 0:05:48 | |
At Santa Cruz, California, all these ingredients come together perfectly. | 0:06:00 | 0:06:06 | |
Thousands of miles of ocean to build up all that energy, | 0:06:06 | 0:06:09 | |
and then the perfect sea bed | 0:06:09 | 0:06:10 | |
to create monster breakers like these. | 0:06:10 | 0:06:13 | |
It's no wonder one sport has made its home here. | 0:06:18 | 0:06:22 | |
Surfing. | 0:06:22 | 0:06:24 | |
Leo and I are here to have a go, and we've got two very special teachers. | 0:06:27 | 0:06:31 | |
Sam, 12, and Ben, 15, have lived next to the ocean all their lives. | 0:06:37 | 0:06:42 | |
They've been surfing since they were five and are now Junior Champions. | 0:06:46 | 0:06:51 | |
They're pretty good. | 0:06:52 | 0:06:54 | |
Their challenge today is to get Clare and I doing this... | 0:06:55 | 0:06:59 | |
..Well, maybe. | 0:07:00 | 0:07:01 | |
-I'm Leo. -Ben. -Nice to meet you, Ben. -Sam. -Hi, Sam, how you doing? | 0:07:07 | 0:07:10 | |
-So, you're going to teach us how to surf? -Yeah, it should be fun. | 0:07:10 | 0:07:14 | |
-So, do you guys surf every day? -Yeah. | 0:07:14 | 0:07:17 | |
And what makes it so fun | 0:07:17 | 0:07:19 | |
that you can surf on the coldest day in winter? | 0:07:19 | 0:07:22 | |
You just get good waves | 0:07:22 | 0:07:24 | |
and it gets you happy when you do good turns. | 0:07:24 | 0:07:27 | |
By following the surf forecasts online, | 0:07:28 | 0:07:31 | |
the boys know in advance what the sea conditions are going to be like. | 0:07:31 | 0:07:35 | |
But sometimes this sea gets dangerous, | 0:07:35 | 0:07:38 | |
and that's where years of experience come in. | 0:07:38 | 0:07:41 | |
It's important to understand where to be, | 0:07:41 | 0:07:44 | |
so you don't get caught in a dangerous situation. | 0:07:44 | 0:07:47 | |
And also you just never want to turn your back to the ocean | 0:07:47 | 0:07:49 | |
because you'll never know if, like, a big wave is going to take you out. | 0:07:49 | 0:07:53 | |
-Trying to read the waves. -Your board doesn't want to be | 0:07:53 | 0:07:55 | |
between you and the wave or, like, it's going to hit you. | 0:07:55 | 0:07:59 | |
Today, the sea is fairly calm, but the waves off this coast | 0:08:00 | 0:08:03 | |
are capable of smashing boats and surfboards in two | 0:08:03 | 0:08:06 | |
with their awesome force. | 0:08:06 | 0:08:08 | |
There's no way you'd get me out in a sea like that! | 0:08:08 | 0:08:10 | |
If you want to harness the energy of a wave on a surfboard, | 0:08:15 | 0:08:18 | |
you have to paddle yourself up to speed | 0:08:18 | 0:08:21 | |
and leap from a lying position to standing up. | 0:08:21 | 0:08:24 | |
Sam and Ben make it look very easy. | 0:08:24 | 0:08:26 | |
Something tells me it isn't... | 0:08:26 | 0:08:29 | |
So, if you're laying down on the board like this...paddling... | 0:08:31 | 0:08:34 | |
whatever foot you put forward... | 0:08:34 | 0:08:37 | |
I don't think I could even do that. | 0:08:37 | 0:08:39 | |
Let's have a go. | 0:08:39 | 0:08:40 | |
I don't think we're going to be the next World Champions! | 0:08:40 | 0:08:43 | |
Too far forward, your nose is going to dig into the water | 0:08:46 | 0:08:48 | |
-and you'll face-plant. -Woo-hoo! Going to be fun! | 0:08:48 | 0:08:52 | |
You're getting there, but you're going to need a lot of practice | 0:08:54 | 0:08:58 | |
-before you get in the ocean. -'I think he may be right.' | 0:08:58 | 0:09:02 | |
OK, nice one. | 0:09:02 | 0:09:04 | |
But, somehow, we persuade them to let us loose in the ocean. | 0:09:04 | 0:09:08 | |
We head off to a beginners' beach where the boys learned to surf. | 0:09:08 | 0:09:12 | |
Conditions are perfect, waves of about 1.5 metres. | 0:09:13 | 0:09:16 | |
Easy for Sam and Ben, | 0:09:17 | 0:09:19 | |
but they look like skyscrapers to us as we paddle out. | 0:09:19 | 0:09:22 | |
After a few failed attempts to catch a wave, we're going nowhere. | 0:09:27 | 0:09:31 | |
But, eventually, with a friendly shove from Ben, | 0:09:35 | 0:09:38 | |
I get up on the wave. | 0:09:38 | 0:09:40 | |
Sort of.. | 0:09:40 | 0:09:41 | |
The energy pushes me hundreds of metres into the shore, | 0:09:41 | 0:09:45 | |
it's an amazing feeling. | 0:09:45 | 0:09:47 | |
Now, it's Leo's turn, and he has to go one better and stand up. | 0:09:48 | 0:09:52 | |
Show off! | 0:09:55 | 0:09:56 | |
-Nice job. -You guys were amazing. | 0:10:03 | 0:10:07 | |
Without you two I just wouldn't have even got in the water. | 0:10:07 | 0:10:10 | |
Yeah, you did really good. That one, you got in it. | 0:10:10 | 0:10:13 | |
Sam, you're amazing! 12-year-old kid teaching me how to surf. | 0:10:13 | 0:10:17 | |
-You rock! -Got it first time! | 0:10:17 | 0:10:19 | |
I can't believe the immense power of those waves. | 0:10:21 | 0:10:25 | |
It was just incredible. | 0:10:25 | 0:10:26 | |
And to think that thing travelled all the way across the ocean | 0:10:26 | 0:10:29 | |
and just for that split second, you get to ride that force. | 0:10:29 | 0:10:32 | |
-It's amazing, isn't it? -It's better than that paddling! | 0:10:32 | 0:10:35 | |
I want to go and get another one! | 0:10:35 | 0:10:36 | |
-High-five! -High-fives back! | 0:10:36 | 0:10:39 | |
Still to come, Leo sees if he has what it takes to beat | 0:10:39 | 0:10:43 | |
the ocean's hidden menace - the rip current. | 0:10:43 | 0:10:46 | |
Feels like I'm going nowhere! | 0:10:47 | 0:10:49 | |
Oceans cover 71% of the Earth's surface | 0:10:51 | 0:10:54 | |
and contain 97% of the planet's water. | 0:10:54 | 0:10:57 | |
The energy carried by waves means lots of fun for surfers | 0:10:57 | 0:11:00 | |
and, as we now know, waves don't actually move the water. | 0:11:00 | 0:11:04 | |
Think about the last time you went to the seaside. | 0:11:04 | 0:11:07 | |
Throughout the day, the water level changes | 0:11:07 | 0:11:11 | |
causing the beach to shrink and grow. | 0:11:11 | 0:11:13 | |
This is the tide coming in and out. | 0:11:13 | 0:11:15 | |
6,000 miles away from Santa Cruz in California is the UK, | 0:11:17 | 0:11:21 | |
a place where tides are a very big deal. | 0:11:21 | 0:11:24 | |
We're in South Wales. | 0:11:26 | 0:11:28 | |
Behind us is the Severn Estuary, | 0:11:28 | 0:11:30 | |
the mouth of Britain's longest river. | 0:11:30 | 0:11:32 | |
The harbour here at the moment is completely full of water. | 0:11:32 | 0:11:36 | |
But if we were just to wait another six hours, | 0:11:36 | 0:11:40 | |
the sea level's going to drop an incredible 12 metres. | 0:11:40 | 0:11:43 | |
To this. It's incredible. | 0:11:46 | 0:11:48 | |
All of this variation in sea level is due to tides. | 0:11:48 | 0:11:52 | |
And we're here to find out how they work. | 0:11:52 | 0:11:54 | |
Tides are one of the great forces on our planet. | 0:11:58 | 0:12:01 | |
Every day, most coastlines | 0:12:01 | 0:12:04 | |
experience two high tides and two low tides. | 0:12:04 | 0:12:06 | |
The driving force behind this constant change is gravity. | 0:12:09 | 0:12:13 | |
What's going to happen if I throw this ball into the sky? | 0:12:17 | 0:12:21 | |
Is it going to stay there, is it going to go upwards? | 0:12:22 | 0:12:25 | |
No, we know what's going to happen. | 0:12:25 | 0:12:27 | |
It's going to fall to the ground. | 0:12:27 | 0:12:29 | |
That's because it's being pulled by a force called gravity | 0:12:29 | 0:12:33 | |
drawing us all into the centre of the Earth. | 0:12:33 | 0:12:35 | |
It keeps me standing here, it's dropped the ball to the ground | 0:12:35 | 0:12:38 | |
and it also keeps the oceans in place. | 0:12:38 | 0:12:40 | |
But we also know the oceans don't stay exactly where they are. | 0:12:43 | 0:12:47 | |
They are constantly on the move, | 0:12:47 | 0:12:49 | |
coming in and going out with the motion of the tides. | 0:12:49 | 0:12:52 | |
Now, why is that? | 0:12:52 | 0:12:54 | |
If you imagine this is the Earth with its own gravitational force, | 0:12:54 | 0:12:58 | |
there's something missing here | 0:12:58 | 0:13:01 | |
and that's up there in the sky. | 0:13:01 | 0:13:03 | |
The moon. | 0:13:03 | 0:13:04 | |
The moon travels round the Earth in one month | 0:13:05 | 0:13:09 | |
and the moon, as a planet, has its own gravitational force | 0:13:09 | 0:13:13 | |
but it's much weaker than that of the bigger Earth, | 0:13:13 | 0:13:16 | |
but it's still strong enough to affect the oceans. | 0:13:16 | 0:13:19 | |
As the moon moves around the Earth throughout each month, | 0:13:19 | 0:13:24 | |
it pulls the oceans slightly towards it, helping to cause the tides. | 0:13:24 | 0:13:28 | |
But there's another thing to think about. | 0:13:28 | 0:13:32 | |
Imagine this is us on the Earth. | 0:13:32 | 0:13:34 | |
The Earth is constantly spinning, | 0:13:34 | 0:13:36 | |
giving us one day and one night every 24 hours. | 0:13:36 | 0:13:39 | |
So, every 24 hours the Earth moves twice | 0:13:41 | 0:13:43 | |
through the deep water giving us high tides, | 0:13:43 | 0:13:46 | |
and twice through the shallow water giving us low tides. | 0:13:46 | 0:13:49 | |
The difference between the height of a high tide | 0:13:51 | 0:13:54 | |
and a low tide is called a tidal range. | 0:13:54 | 0:13:57 | |
Almost nowhere in the world sees a bigger tidal range | 0:13:57 | 0:14:01 | |
than here in the Severn Estuary. | 0:14:01 | 0:14:03 | |
That's because of its distinctive funnel shape. | 0:14:03 | 0:14:06 | |
If you've got Wales here and England there, | 0:14:06 | 0:14:09 | |
the tide is being forced up this funnel-shape river mouth, like so. | 0:14:09 | 0:14:14 | |
There's only one thing going to happen. | 0:14:14 | 0:14:16 | |
The water mass is moving in and in as the tide rises, | 0:14:19 | 0:14:23 | |
but it's getting funnelled in and there's land either side - | 0:14:23 | 0:14:26 | |
it can't go anywhere, | 0:14:26 | 0:14:28 | |
so it builds up, just like this sand here, | 0:14:28 | 0:14:30 | |
and builds up and builds up and builds up. | 0:14:30 | 0:14:32 | |
So, around about this part of the estuary, | 0:14:32 | 0:14:34 | |
that's where you get the highest tides, | 0:14:34 | 0:14:37 | |
because it's being forced into this funnel shape. | 0:14:37 | 0:14:39 | |
This massive tidal range can be used to great effect by ports, | 0:14:42 | 0:14:46 | |
because it means, at high tide, | 0:14:46 | 0:14:48 | |
you can get enormous ships in and out of docks, | 0:14:48 | 0:14:51 | |
like this one in Bristol. | 0:14:51 | 0:14:53 | |
But you don't have long to do it. | 0:14:53 | 0:14:55 | |
Every day, thousands of tonnes of cargo | 0:14:59 | 0:15:02 | |
come in and out of this massive dock. | 0:15:02 | 0:15:05 | |
They can bring anything from cars, | 0:15:05 | 0:15:07 | |
coal, even toys, to Britain. | 0:15:07 | 0:15:09 | |
But getting the huge ships that carry all of this | 0:15:10 | 0:15:13 | |
in and out of the docks is a real assault course because of the tides. | 0:15:13 | 0:15:18 | |
By measuring the distance of the moon from the Earth | 0:15:18 | 0:15:21 | |
and understanding the shape of the sea bed, | 0:15:21 | 0:15:23 | |
scientists can predict for many years ahead | 0:15:23 | 0:15:26 | |
when we will have high and low tides. | 0:15:26 | 0:15:28 | |
This channel controls the shipping in and out of the dock. | 0:15:30 | 0:15:34 | |
Now, the level of water in the dock always stays high | 0:15:34 | 0:15:37 | |
because of these giant gates, they lock the water back. | 0:15:37 | 0:15:41 | |
But at low tide, we've got a problem. | 0:15:41 | 0:15:43 | |
Look at the other side here. | 0:15:43 | 0:15:44 | |
You can see the water level's down to less than a metre, | 0:15:44 | 0:15:48 | |
you can see mud banks over there. | 0:15:48 | 0:15:50 | |
There's no way we're going to get a large ship into the docks | 0:15:50 | 0:15:53 | |
when the tide is low. | 0:15:53 | 0:15:55 | |
There's only one way to do that - | 0:15:55 | 0:15:57 | |
wait until the tide has risen high enough | 0:15:57 | 0:15:59 | |
and very carefully guide the ship in. | 0:15:59 | 0:16:01 | |
I'm here to meet Jerry. | 0:16:03 | 0:16:05 | |
-Hello! -Nice to see you. Welcome aboard. -Great! | 0:16:05 | 0:16:08 | |
He's like an air-traffic controller for ships. | 0:16:08 | 0:16:11 | |
His job is to get as many ships into port as possible | 0:16:11 | 0:16:14 | |
during the small window of opportunity. | 0:16:14 | 0:16:17 | |
He needs to know exactly when the tide will be high | 0:16:17 | 0:16:19 | |
and when it will be low. | 0:16:19 | 0:16:22 | |
Harbour control... | 0:16:22 | 0:16:23 | |
We're heading out into the estuary to meet a huge car container | 0:16:23 | 0:16:28 | |
that's come all the way from Spain. | 0:16:28 | 0:16:30 | |
She's quite a big ship, so she's probably about 35-40,000 tonnes. | 0:16:30 | 0:16:33 | |
Big ship, 160-odd metres long. | 0:16:33 | 0:16:35 | |
-You're not going to sail that through here?! -Oh, yes! | 0:16:35 | 0:16:38 | |
We have to drop nearly ten metres in the lock - | 0:16:40 | 0:16:42 | |
that's the same as a three-storey building - | 0:16:42 | 0:16:45 | |
to get to the same water level as out in the estuary. | 0:16:45 | 0:16:48 | |
But once we're out there, | 0:16:48 | 0:16:50 | |
it's obvious that the tide is rising rapidly. | 0:16:50 | 0:16:53 | |
Wow, the estuary really is alive. | 0:16:55 | 0:16:57 | |
You can see the water just rushing its way up the river. | 0:16:57 | 0:17:01 | |
Look at the buoy over there, it's being bent towards inland. | 0:17:01 | 0:17:04 | |
That's indicating that thousands and thousands of tonnes of water | 0:17:04 | 0:17:07 | |
are working their way now directly up towards the port. | 0:17:07 | 0:17:11 | |
The estuary is filling up at an amazing three metres per hour | 0:17:13 | 0:17:17 | |
and, right on cue, our ship comes around the headland. | 0:17:17 | 0:17:20 | |
SHIP FOGHORN BLOWS | 0:17:20 | 0:17:22 | |
Dougal, there she is. That's your first sight of her. | 0:17:22 | 0:17:25 | |
There she blows! | 0:17:25 | 0:17:26 | |
But getting her into dock won't be easy. | 0:17:28 | 0:17:31 | |
The fast-moving water heading up the estuary | 0:17:31 | 0:17:34 | |
is trying to push the ship past the entrance to the port. | 0:17:34 | 0:17:37 | |
This is the really critical moment. | 0:17:38 | 0:17:40 | |
And this chunk of metal is being safely guided through | 0:17:41 | 0:17:44 | |
-that very small gap, essentially using the tides. -That's right. | 0:17:44 | 0:17:49 | |
Without the tidal range we have here, she would not get in there. | 0:17:49 | 0:17:52 | |
One more ship has safely run the assault course | 0:17:56 | 0:18:00 | |
of a fast-rising tide. | 0:18:00 | 0:18:01 | |
But it's not just boats who have to battle the tides in this estuary. | 0:18:05 | 0:18:09 | |
People regularly get caught out, too. | 0:18:09 | 0:18:12 | |
Like here at Sully Island, which lies 200m off the South Wales coast. | 0:18:12 | 0:18:17 | |
At low tide, it's possible to walk over to it. | 0:18:17 | 0:18:21 | |
But in the last five years, | 0:18:21 | 0:18:23 | |
more than 50 people have been cut off by the lightning-quick tides, | 0:18:23 | 0:18:27 | |
keeping the local RNLI team, like Nicola, very busy. | 0:18:27 | 0:18:32 | |
What we're stood on here is the causeway | 0:18:33 | 0:18:36 | |
and this is the area that gets cut off by the tide. | 0:18:36 | 0:18:38 | |
When the tide comes in, it covers this area so you couldn't cross. | 0:18:38 | 0:18:41 | |
In just a couple of hours' time | 0:18:41 | 0:18:42 | |
there will be six metres of water above us, | 0:18:42 | 0:18:45 | |
so a very, very dangerous area. | 0:18:45 | 0:18:47 | |
Nicola wants to show me exactly how quick the water arrives | 0:18:47 | 0:18:51 | |
and why YOU should never ignore warnings about tides. | 0:18:51 | 0:18:55 | |
'I think I'm going to get my feet wet, | 0:18:55 | 0:18:58 | |
'so she's kindly kitted me out in a warm dry suit.' | 0:18:58 | 0:19:02 | |
-Wow, it is surrounding us quite quickly, isn't it? -It is. | 0:19:04 | 0:19:08 | |
-How much time do we have? -About ten minutes before we're covered here. | 0:19:08 | 0:19:11 | |
The plan is to see how long I can keep my footing | 0:19:16 | 0:19:19 | |
as the water rushes to fill the channel | 0:19:19 | 0:19:21 | |
between the island and the mainland. | 0:19:21 | 0:19:23 | |
The guys are on standby. | 0:19:23 | 0:19:25 | |
So, bring on the tide! | 0:19:25 | 0:19:27 | |
I've got a highly-trained lifeboat crew watching me, | 0:19:27 | 0:19:30 | |
so this is definitely not something you should ever try. | 0:19:30 | 0:19:34 | |
I've only been here a couple of minutes, | 0:19:34 | 0:19:36 | |
and I can't believe how fast the water's already surrounding me. | 0:19:36 | 0:19:40 | |
I'm really glad I've got my wellies on. Look at this! | 0:19:40 | 0:19:44 | |
This is incredible! This water is rushing up the channel so quickly | 0:19:44 | 0:19:48 | |
that the sea level is rising by 20cm every five minutes. | 0:19:48 | 0:19:52 | |
I'm experiencing one of the world's fastest tides. | 0:19:53 | 0:19:56 | |
It's getting deeper, | 0:19:58 | 0:20:00 | |
bashing against my legs and you've got the wind to contend with, too. | 0:20:00 | 0:20:04 | |
I'm keeping calm, because I've got the safety guys on hand. | 0:20:04 | 0:20:08 | |
Five minutes in, and I'm struggling to keep my footing | 0:20:08 | 0:20:12 | |
on the slippy rocks. The water's almost at the top of my legs. | 0:20:12 | 0:20:16 | |
It's starting to get a little bit scary, actually. | 0:20:17 | 0:20:20 | |
OK, this is all becoming a bit of a struggle, | 0:20:20 | 0:20:23 | |
so it's time for the guys to come and get me out. | 0:20:23 | 0:20:26 | |
I'm ready! | 0:20:27 | 0:20:28 | |
'It's a big relief to be pulled to safety.' | 0:20:36 | 0:20:40 | |
Thanks, guys! | 0:20:40 | 0:20:42 | |
Whoa! Whoa, whoa, whoa! | 0:20:42 | 0:20:43 | |
'It was very scary being cut off like that. | 0:20:43 | 0:20:47 | |
'If you go to the beach, remember to make sure an adult knows | 0:20:47 | 0:20:50 | |
'when the tides are coming in.' | 0:20:50 | 0:20:52 | |
I really wasn't expecting it to be that powerful. | 0:20:56 | 0:20:59 | |
A few minutes ago, it was trickling around my feet, | 0:20:59 | 0:21:02 | |
and then, before you know it, | 0:21:02 | 0:21:03 | |
two, three minutes later, it's up to your waist | 0:21:03 | 0:21:06 | |
and it's choppy and it's powerful and you've got the wind. | 0:21:06 | 0:21:09 | |
Without these guys, I would've been in a lot of trouble. | 0:21:12 | 0:21:15 | |
The work done by life-savers like the RNLI | 0:21:20 | 0:21:23 | |
keeps people out of harm's way at the seaside. | 0:21:23 | 0:21:25 | |
It's no different back in California, | 0:21:27 | 0:21:29 | |
where staying safe in the ocean is priority number one. | 0:21:29 | 0:21:33 | |
The hundreds of lifeguards who work here | 0:21:35 | 0:21:38 | |
are trained to be the best in the business. | 0:21:38 | 0:21:41 | |
Today's the annual try-out for Santa Cruz lifeguards. | 0:21:41 | 0:21:45 | |
These guys have to prove their swimming | 0:21:45 | 0:21:47 | |
and life-saving skills are up to the job. | 0:21:47 | 0:21:50 | |
That's because out in these oceans, | 0:21:50 | 0:21:51 | |
there's a hidden menace known as rip currents, | 0:21:51 | 0:21:54 | |
strong currents that pull people out to sea | 0:21:54 | 0:21:56 | |
responsible for 80% of all the US lifeguards' rescues. | 0:21:56 | 0:21:59 | |
Part of the team here is Gigi. | 0:22:01 | 0:22:04 | |
She's been patrolling these beaches for eight years, | 0:22:04 | 0:22:07 | |
so knows exactly how to spot a lurking rip current. | 0:22:07 | 0:22:10 | |
She's taking me to a notorious beach, | 0:22:12 | 0:22:15 | |
where swimmers and surfers face their threat every day. | 0:22:15 | 0:22:18 | |
My job as a lifeguard is to be constantly looking to see | 0:22:21 | 0:22:24 | |
if rip currents are being formed, | 0:22:24 | 0:22:26 | |
because that is one of the number-one rescues on the beach. | 0:22:26 | 0:22:28 | |
Rip currents can form on any sandy beach. | 0:22:28 | 0:22:32 | |
Powerful waves pound the shoreline... | 0:22:33 | 0:22:36 | |
..they break, releasing huge amounts of energy | 0:22:40 | 0:22:43 | |
but then all that water wants to flood back out to sea. | 0:22:43 | 0:22:46 | |
Sometimes a narrow channel forms in the sandy sea bed, | 0:22:49 | 0:22:52 | |
and this is the route that the water uses | 0:22:52 | 0:22:54 | |
to surge back out to sea in a rip current. | 0:22:54 | 0:22:57 | |
So a fast-moving current is actually flowing AWAY from the beach. | 0:22:57 | 0:23:01 | |
And when a swimmer gets caught in one, | 0:23:03 | 0:23:05 | |
they won't realise it until they look back at the beach | 0:23:05 | 0:23:07 | |
and see how far they've travelled out to sea. | 0:23:07 | 0:23:10 | |
It doesn't necessarily suck you under, | 0:23:10 | 0:23:12 | |
-it more sucks you straight out. -And that can be pretty dangerous? | 0:23:12 | 0:23:15 | |
It can be extremely dangerous, | 0:23:15 | 0:23:17 | |
and all your energy will force you to get tired | 0:23:17 | 0:23:20 | |
and that's how a lot of drownings are caused. | 0:23:20 | 0:23:22 | |
It all sounds pretty scary. | 0:23:23 | 0:23:25 | |
But for my extreme challenge today, Gigi's got a plan to show me | 0:23:25 | 0:23:29 | |
how helpless it feels to be trapped in a powerful rip current. | 0:23:29 | 0:23:32 | |
It's too dangerous to swim in one for real, | 0:23:36 | 0:23:39 | |
but out here in the bay, | 0:23:39 | 0:23:40 | |
the conditions are perfect for our experiment. | 0:23:40 | 0:23:43 | |
Well, what we're going to do is put your bungee cord | 0:23:45 | 0:23:48 | |
around your waist and while the boat drifts, | 0:23:48 | 0:23:51 | |
you'll be pulling, as if you're being pulled in the current. | 0:23:51 | 0:23:54 | |
My challenge is to swim the 200 metres to shore, | 0:23:56 | 0:23:58 | |
that's eight lengths of an ordinary swimming pool, | 0:23:58 | 0:24:01 | |
with an elastic cord tying me to our boat. | 0:24:01 | 0:24:04 | |
The extra energy I'll need to tow the boat behind me | 0:24:06 | 0:24:08 | |
is going to feel just like swimming against a rip current. | 0:24:08 | 0:24:12 | |
It's going to be very, very tough. | 0:24:12 | 0:24:14 | |
And I hate cold water. | 0:24:14 | 0:24:16 | |
OK, I'm going in, Gigi. | 0:24:24 | 0:24:26 | |
-All right, Leo, you can do it. -Oh, looks cold! | 0:24:26 | 0:24:29 | |
-Remember to stay calm. -Ahh, it's freezing! -Don't panic! -Oohhh! | 0:24:29 | 0:24:32 | |
Although the sea is calm, this is a dangerous swim. | 0:24:35 | 0:24:38 | |
Pulling the weight of the boat behind me | 0:24:38 | 0:24:40 | |
is going to tire me out very quickly, | 0:24:40 | 0:24:42 | |
so Gigi will be my own personal lifeguard | 0:24:42 | 0:24:44 | |
alongside on her rescue board. | 0:24:44 | 0:24:46 | |
I make a good start. | 0:24:56 | 0:24:57 | |
Normally, I could swim 200 metres fairly easily, | 0:24:58 | 0:25:01 | |
but as the elastic extends, | 0:25:01 | 0:25:02 | |
I start to feel the pull of the boat behind me. | 0:25:02 | 0:25:05 | |
Feels like I'm going nowhere! | 0:25:10 | 0:25:12 | |
'I'm starting to tire and lose my technique, | 0:25:13 | 0:25:16 | |
'just like being in a real rip current.' | 0:25:16 | 0:25:19 | |
Keep going, Leo, you're doing good! | 0:25:21 | 0:25:23 | |
The best way to escape if this was real | 0:25:24 | 0:25:26 | |
would be to swim at right angles to the shore, like this... | 0:25:26 | 0:25:30 | |
But I don't have that choice today. | 0:25:30 | 0:25:32 | |
After just one and a half minutes, | 0:25:35 | 0:25:36 | |
I've only travelled 20 metres but I'm exhausted. | 0:25:36 | 0:25:40 | |
Fighting against the bungee has sapped all my energy. | 0:25:41 | 0:25:44 | |
So, Gigi comes to the rescue. | 0:25:47 | 0:25:50 | |
I feel like a drowned rat...! | 0:25:57 | 0:25:58 | |
If that had been a real rip, | 0:26:03 | 0:26:05 | |
I'd never have made it back to the shore. | 0:26:05 | 0:26:07 | |
Thank goodness Gigi was here. | 0:26:07 | 0:26:10 | |
These things are dangerous. | 0:26:10 | 0:26:12 | |
He did good. He gave a good effort, he tried hard. | 0:26:12 | 0:26:15 | |
It just goes to show that swimming straight into shore | 0:26:15 | 0:26:18 | |
is not an easy way to exit a rip current. | 0:26:18 | 0:26:21 | |
This was always going to be a tough challenge. | 0:26:23 | 0:26:25 | |
I've only managed to swim 20 metres, | 0:26:25 | 0:26:28 | |
a fraction of the distance to shore. | 0:26:28 | 0:26:30 | |
Fighting against a rip current is a battle you're not going to win. | 0:26:30 | 0:26:34 | |
The Fierce Earth team have been up close | 0:26:39 | 0:26:41 | |
with the living, breathing ocean. | 0:26:41 | 0:26:43 | |
The power of waves can be fun, | 0:26:45 | 0:26:47 | |
but you must never turn your back on them. | 0:26:47 | 0:26:50 | |
Always be aware of hidden rip currents. | 0:26:51 | 0:26:54 | |
Tides creep up and down under the pull of gravity. | 0:26:56 | 0:26:59 | |
Their power can helps ships into port, | 0:26:59 | 0:27:02 | |
but if you don't stay alert, their rapid rise can catch you out. | 0:27:02 | 0:27:06 | |
It's getting deeper, bashing against my legs. | 0:27:07 | 0:27:10 | |
Where the land meets the sea... | 0:27:10 | 0:27:12 | |
..we've learned the Earth can get very fierce. | 0:27:14 | 0:27:17 | |
In the very special next episode of Fierce Earth... | 0:27:20 | 0:27:23 | |
Leo chooses his most extreme moments ever. | 0:27:23 | 0:27:26 | |
Plus, an all-new exclusive challenge. | 0:27:26 | 0:27:29 | |
I'm going to take to the skies and fly like a bird. | 0:27:29 | 0:27:32 | |
He's saving the fiercest till last. | 0:27:32 | 0:27:34 |