- [Narrator] Coastlines have captured the human imagination since the dawn of history inspiring us to venture beyond the horizon.

Along coasts, one element ends and another begins and with that nature's artistry seems endless.

No two days are ever the same on a coastline, the only thing that remains a constant, is the timeless power of the sea.

(dramatic music) Punctuating coastlines around the globe, harbors are one of the most significant natural features in the landscape.

Sheltered bodies of water, that have long been important to maritime trade.

There are well over four and a half thousand harbors world-wide, wonders of nature that have allowed many great civilizations throughout history, to prosper and thrive.

Dubai has been a busy middle-eastern port-city for more than a thousand years.

Alexandria in Egypt is older still.

And while Sydney, on the east coast of Australia, is a relative newcomer to the list of the world's great harbor cities, it eclipses them all with its natural beauty.

Between north and south head, the Pacific Ocean spills into a drowned river valley that stretches 21 kilometers inland, creating the largest natural harbor in the world.

The amount of water in Sydney Harbour is actually an official Australian unit of measurement referred to as one Sydharb.

And that's roughly enough water to fill 200,000 Olympic-sized swimming pools.

There are hundreds of bays and inlets indenting the 240 kilometer harbor coastline.

A fair measure of which remains protected by national parks and local reserves providing habitat for some of Sydney's wilder residents.

A colony of bats that rule the roost in the botanic gardens behind the Opera House, golden-faced plovers and seagulls nesting on the harbor islands and a small population of endangered weedy sea dragons holding their own in the marine vegetation along with no fewer than 586 different species of fish, twice the number recorded from the entire coastal waters of the United Kingdom.

There are dozens of small, sandy beaches within Sydney Harbour but even their popularity pales, when compared to those that lie on the seaward side of the city.

Vertical sandstone cliffs and rocky headlands define the Pacific Ocean coastline of Sydney, broken by golden sand beaches that have come to symbolize the Australian way of life.

The surf here is legendary, attracting board riders from all over the world and the beaches are equally renowned, famed as much for their cultural heritage, as their natural beauty.

Exposed to waves and salt spray, the sandstone cliffs along Sydney's coastline have eroded over millions of years, leaving behind a wide, flat rock platform and a series of spectacular beaches, made up of tiny grains of rocks and minerals, worn down by the constant pounding of wind and waves.

These sandy sediments fall into the Pacific Ocean, and are moved around and redeposited along the coast by waves and currents.

But an even greater force exerting its influence on our oceans is the tide, the cyclic rising and falling of the sea.

(dramatic music) Every grain of sand and molecule of water in the ocean, responds to the gravitational pull of the sun and moon.

Because the moon is so much closer to the Earth, it is twice as powerful as the Sun, affecting the ebb and flow of the tide as it waxes and wanes.

When the tide goes out on this 15 and a half mile stretch of western Australia's coastline, a secret from the deep past is revealed.

Thousands of footprints that were made by dinosaurs, 130 million years ago.

The landscape was very different back then, a vast river plain opening into a wide belt of tidal deltas, brackish lagoons and estuaries that created a bed of soft, muddy sediments, the perfect medium for preserving dinosaur tracks.

Over time, these footprints were covered by dry sediments, which then lithified, or compacted into rock.

But thanks to the process of erosion and weathering this protective covering has since worn away revealing the fossilized tracks.

Most of them occur below the high water mark and at Gantheaume point near Broome, they can only be accessed on extremely low tides.

This is the only place in Australia where Sauropod tracks have been found made by creatures with elephant-like feet.

30 meters long from head to tail.

In 2016, the largest Sauropod footprint in the world was found on this stretch of coast, along with tracks made by 20 other dinosaur species.

Making this the richest dinosaur track site on Earth.

Another wonder that's revealed by the full moon during summer along this part of the north-western coast, occurs across the tidal flats of Roebuck Bay.

As the tide drops, an extraordinary natural phenomenon occurs, an optical illusion that gives the impression of a staircase leading to the moon.

Further north, the pull of the tide has an even more dramatic consequence, creating a horizontal waterfall in the middle of the Buccaneer Archipelago.

This group of islands in Talbot Bay, just off the Kimberley coastline, is wild and remote, a breath-taking location for one of nature's more remarkable wonders.

The shape of any coastline will strongly affect the nature and size of the local tides and here they are a force to be reckoned with!

The rocks making up the islands in the archipelago are over two billion years old, an extension of the mainland land-mass, cut off when sea-levels rose.

Because the continental shelf here is very wide and shallow, tide wave, as it moves towards the land, increases in height.

What began as an 18 centimeter high tide in the deep ocean amplifies as it moves towards the coast and by the time it reaches the two narrow gorges that cleave through McLarty Ranges, the tide can be 10 meters high!

This massive tidal movement creates a waterfall effect as the water builds up in front of each gap, faster than it can flow through either of them.

During the highest tides, one million liters of water pour through both gorges every second creating a spectacular sight from sea level, or the air.

Horizontal Falls is just one wild wonder, along a coastline crammed with dozens.

There are plenty of vertical falls here as well, even some you can inch a boat under.

Billowing from soaring cliffs that enclose huge tidal gorges, that cut into the untamed world of the Kimberley an ancient plateau, roughly three times the size of England.

The plateau rose above the sea 1800 to 2400 million years ago and is full of rock formations that bear witness to its long and varied geological past.

But tucked deep within their hidden cracks and overhangs are paintings some anthropologists say represent the oldest figurative art in the world.

They're known as Gwion Gwion, or the Bradshaw paintings in honor of the first European explorer to see them.

They're thought to have been created by the ancestors of indigenous Australians, who crossed the sea from Timor, some 60,000 years ago.

Very few people live along this isolated coastline today and its treasures are often difficult to access.

But every step forward along the Kimberley coast, is a quantum leap back in time offering up small pieces of the puzzle, that help us to make sense of the past.

(dramatic music) Thanks to its countless off-shore islands, myriad bays and deep inlets, Canada lays claim to having the longest coastline in the world, a daunting 202,080 kilometers, roughly five times the circumference of the Earth!

Bordered by the Atlantic, Pacific and Arctic oceans, Canada boasts many unique geological assets.

Including these precarious formations, that line the Bay of Fundy, eroded by tides that shift a colossal 16 meters a day.

Even their beauty is regularly eclipsed by all the wildlife that frequents the coast.

More than 30 species of whales cruise by Canada's extensive Pacific coastline.

At any given time in summer, there could be 300 to 400 whales in the Bay of Fundy alone, drawn by the enormous amounts of krill and plankton, that wash in on those powerful tides.

12 species have been sighted here but by far the most regular visitor, is the humpback whale.

Growing to 18 meters in length and weighing up to 45 tons they're big whales with gargantuan appetites consuming two thousand to two and a half thousand kilograms of food in a day, roughly the weight of half an elephant.

Killer whales or orcas occasionally put in an appearance at Fundy but an even better place to account of them in their natural environment is off Telegraph Cove, in the Johnstone Strait which separates the northern part of Vancouver Island from the rest of British Columbia.

Vancouver Island is the largest island on the entire west coast of North America with a 3,400 kilometer coastline of its own.

The waters around it and the skies above form a giant wildlife sanctuary.

When the tide rushes the water up against a bank of rocks in this inlet, any fish caught up in the turbulent water, are knocked unconscious.

When they float to the surface, bald eagles swoop in for an easy feed.

Despite their name killer whales are not true whales, rather, they're members of the dolphin family.

Famous for their ability to hunt in groups, northern transient killer whales dine exclusively on marine mammals such as seals.

But resident killer whales only eat squid and fish and in this part of the world, their favorite prey is salmon!

The waters on and around Vancouver Island are so well stocked with this type of fish, it's popularly known as the salmon capital of the world attracting anglers from around the globe.

Their greatest challenge of course, is having to compete with orcas for a share of the spoils not to mention any number of black bears and grizzlies!

Most of a bear's diet is a mix of berries and grasses that grow deep in the forests.

But in spring, when the salmon are running upstream to breed they make their way down to the shorelines.

Individual bears have different strategies for catching salmon passed down from their mothers but all need to ensure they fill up on protein, before their winter hibernation.

On the opposite side of Canada, on the shores of Hudson Bay, Churchill stakes its claim for hosting the largest and most accessible polar bear population on the planet.

Weighing in at around 680 kilos, polar bears are the Arctic's top predator.

Although all bears can eat meat the polar bear is the only exclusively carnivorous bear.

In autumn they roam along this remote stretch of coastline waiting for Hudson Bay to freeze over giving them better access to seals, their favorite prey.

They are powerful swimmers and will enter the water to catch food but are equally content to scavenge along the shore eating beached whales or dead seals and crabs.

Polar bears are well suited to life in the Arctic.

They have a layer of fat, or blubber, that insulates their bodies from the freezing cold air and water and a thick coat of fur that extends to the soles of their feet helping them to maintain their grip on treacherous ice.

Each hair is translucent but because they reflect the light they appear to be white.

And beneath all that fur, their jet black skin helps them to absorb heat from the sun.

When winter kicks in around Churchill, pregnant female polar bears retreat into dens but males enter a state scientists call a walking hibernation remaining awake and active, yet still living off their reserves of fat.

There is an upside to staying awake in this part of the world through the long, cold winters and that's the chance to bear witness to one of the greatest cosmic light shows on Earth, the Aurora Borealis or Northern Lights.

(dramatic music) While tides exert the strongest influence on oceans waves completely rule the world's coastlines.

They are the ultimate sculptors gnawing away at cliffs and eroding magnificent bays.

Some coastlines such as the Tasman peninsula in Tasmania, Australia, can take quite a battering from the ocean for they are mostly made up of dolerite which is very hard and resistant to erosion.

Having pushed its way up from deep within the Earth as magma, through a thick bed of sandstone, the dolerite cooled slowly, fracturing vertically as it contracted, creating these huge hexagonal columns.

The sandstone that once protected the columns has long worn away leaving these amazing organ-pipe like structures exposed.

In some places they soar 300 meters above the water creating some of the tallest dolerite sea cliffs in the world.

One of the most startling features here at Cape Hauy, is the 90 meter high needle holding its own in the wild southern ocean now, and for many years to come.

Other sea cliffs around the world are not nearly as resistant to erosion such as the dramatic cliffs of Moher, in Ireland.

This rugged stretch of coastline, overlooking the Atlantic Ocean on the west coast of County Clare, is as much an historical landmark as it is a natural wonder.

For this is where ships from the Spanish Armada were first sighted fleeing from their unsuccessful mission to invade England in 1588.

Blown off-course by high winds, as many as 27 ships sank and 9,000 Spanish soldiers lost their lives.

They either drowned at sea, or were killed as they attempted to come ashore.

At their highest point, the cliffs of Moher are 214 meters but many of the tales that surround them are taller still!

There are stories about a mythical, underwater city, tales about witches and corpse-eating eels, and no doubt inspired by one too many pints of Guinness the obligatory account of a love-struck fisherman and a mermaid.

The White Cliffs of Dover an eight kilometer stretch of coastline in the English county of Kent have been immortalized in many a stirring ballad and poem, an enduring symbol of the nation as dear to the British as the Statue of Liberty is to Americans.

Julius Caesar was the first to record a description of them in 55 BC, when he was looking for a suitable place to land and effect the Roman invasion.

The White Cliffs of Dover are also irreversibly linked to the Second World War largely due to the popularity of the song Vera Lynn made so famous.

The cliffs are made of chalk, a fossilized white mud that was formed from the skeletons of minute algae that eons ago would have been floating in the surface waters of the sea.

Movements of the Earth's crust lifted these layered sediments clean out of the water, around 70 million years ago and they have been slowly crumbling away ever since.

Recent studies suggest that the rate of erosion here has quickened considerably in the last 150 years increasing from two to 32 centimeters a year due, in no small part, to rising sea levels and an increase in storm activity.

The bigger the waves that hammer sea cliffs, wherever they may be in the world, the greater the level of erosion.

And most big waves begin out to sea where they are whipped up by the wind.

The highest recorded wave detected by an ocean buoy, measured a colossal 19 meters, from peak to trough.

But even bigger waves are regularly sighted and reported by sailors including one in the North Atlantic that was allegedly 29 meters high roughly the height of an eight story building.

Waves caused by severe weather out to sea, intensify as they move closer to the land creating problems for anyone caught off-guard on the coast.

Before the coastlines of the world were adequately surveyed sailing too close to land in any weather was considered a risky endeavor.

Australia's vast coastline is littered with thousands of vessels whose captains courted such a fate, and paid the price for their poor judgment or bad luck.

Pushed by the wind and waves into rocky headlands and shorelines or running aground on shallow coral reefs or sandbars.

The 130 kilometer stretch of coastline between Cape Otway and Port Fairy in Victoria, had a particularly bad reputation among Australia's early European colonists.

Whether they were destined for Melbourne, Sydney or Brisbane all of the ships sailing in from England during the 1800s, could shave 1200 kilometers off their voyage by threading their way through the eye of the needle, a notorious passage between King Island in the Bass Strait and Cape Otway.

Matthew Flinders, the first person to circumnavigate and map the coastline of Australia said he'd seldom seen a more fearful section of coastline.

In all, some 700 ships have come to grief off the Victorian coast, 180 along this short, but treacherous stretch.

Among them, the Loch Ard after which this narrow gorge has been named.

All but two of the 72 passengers and crew died in that catastrophic accident.

As the Loch Ard smashed into the cliffs her masts and spars crashed onto the deck killing or maiming many on board and stopping others from accessing the ship's life rafts.

The survivors, midshipman Tom Pearce and Irish immigrant, Eva Carmichael managed to make it ashore but the memory of those who perished in the disaster, still lingers on the headland nearby.

When the sea is calm and the breeze gentle, it's difficult to imagine this place as the backdrop to so much tragedy.

Especially since the coastline is better known around the world for its beauty.

Waves from the southern ocean have been pounding into the so-called 12 apostles coastline for eons cutting into its headlands from both sides forming caves that become arches which eventually collapse leaving sea stacks, isolated from the coast.

From the air, you can almost see the coastline retreating as the waves claim two to four centimeters of rock from the land every year breaking it down into rubble and sand.

The harder the rock, the more resistant it is to erosion and the more resistant it is the longer it survives.

Eventually, all the sea stacks that rise above the waves today will cease to exist but the wind and waves will just as surely create others to take their place ensuring the longevity of this dramatic coast for many millions of years to come.

(dramatic music) While the majority of ships wrecked around the world have either smashed into rocks or run aground, there are thousands that owe their watery fate to warfare.

Chuuk Lagoon in Micronesia, in the western Pacific Ocean, is a vast graveyard for World War II wrecks.

Chuuk was the main command center in the Pacific for Japan's naval operations during World War II.

It had four airstrips, a shipyard, and a submarine base and as many as 30,000 troops on site.

To ensure their supremacy in the region, the US and its allies decided to attack Chuuk Lagoon, and attempt to take out the Japanese base and its fleet.

They launched what was, at the time, the largest co-ordinated aerial strike in history.

(dramatic music) [Explosions] And when Operation Hailstone was over, Japan's fire-power was seriously diminished.

In two days, 50 of their ships had been sunk and as many as 250 aircraft in various stages of assembly had been destroyed.

Many of the ships and the occasional tank that fell to the bottom of the lagoon are surprisingly intact as are some of the gas masks and ammunition the Japanese would have had on board.

Other epic World War II battles took place in nearby Palau and its tropical waters are also strewn with the remnants of wrecks from the war.

Many of the 60 ships that were sunk in the area were quickly salvaged and sold off for scrap metal but some remained off the radar for decades including this small, 58 meter supply ship, discovered in Palau's rock islands in 1990.

Nature has claimed this coaster and turned it into a reef, but you can still make out quite a bit of the cargo the ship was carrying including ammunition boxes, rifles and bullets.

The original name of the ship is not known, but locally it's referred to as Helmet Wreck after the stash of helmets that were found in the aft of the ship.

It's almost impossible now to comprehend the scope of the battles that were fought here, in this exquisite, peaceful place.

Clearly one of the more sublime natural wonders in the Pacific below the waterline and above.

There are 445 uninhabited islands in the Rock Islands of Palau, forming a maze of waterways and hidden, turquoise lagoons surrounded by magnificent coral reefs.

The islands are remnants of what was once a vast, exposed limestone reef eroded by pounding surf, tidal action, rainwater, chemically eroding caverns and small mollusks or chitons, chewing away at the intertidal zone, breaking down the limestone, giving the water in some of the land-locked lagoons a milky hue.

The islands harbor the highest concentration of marine lakes in the world, isolated bodies of seawater, cut off from the ocean by land barriers.

Golden jellyfish have made a home for themselves in the lakes that sit in the center of Eil Malk.

With no risk of being eaten, the golden jellyfish have built up in huge numbers, and over time, have all but lost the need to defend themselves so their stinging cells have weakened, making them a safe companion for swimmers.

Typically, jellyfish just float on currents, with no sense of direction but the hundreds of thousands of golden jellyfish living here in Eil Malk migrate across the lake and back every day, following the arc of the sun.

They move by pumping water through their bells propelling themselves into the light which they need, indirectly, to survive.

They rotate anti-clockwise as they move, ensuring an even spread of sunlight across their bodies.

This nourishes the zooxanthellae a tiny algae-like organism that lives within their tissues.

As these organisms photosynthesize, so they can continue to survive, they produce energy as a byproduct which helps to nourish their jellyfish hosts.

Clearly a win-win for each partner in this unusual symbiotic relationship!

As many as eight million jellyfish can live comfortably in the lake but in times of drought, the water becomes noticeably saltier, and in recent years this appears to have affected the population with numbers falling to as few as half a million.

So far, however, when numbers have plummeted, there have been enough jellyfish polyps, toughing it out on the lake floor, to ensure their population recovers when the rains return.

(dramatic music) 40% of the world's population live within 100 kilometers of a coast, some 200 million live within walking distance of the shoreline less than five meters above sea level.

Many depend almost entirely on the natural resources around them including remote island communities such as those along the east coast of the island of New Guinea.

They build their homes out of local timbers felled in the coastal forests.

They process taro and coconut from trees growing along the shoreline.

They harvest crops that don't seem to mind the sandy soils and make a living from the bounty of the sea collecting sea cucumber and fish to sell on the open market.

The real wonder here celebrated in a dance to attract more fish to the region is just how well these communities have managed to hold onto their culture and sustainable way of life even as they become increasingly exposed to the modern world.

The people who live in the Raja Ampat archipelago, just off the western Papua end of the island of New Guinea, are equally dependent on the health of their natural environment, and equally committed to its protection.

Their archipelago is made up of over 1,500 islands, shoals and cays and the territory they protect is enormous, more than 15,500 square miles of land and sea roughly the same size as 10,000,000 soccer fields.

The islands are a geological wonder in their own right, a text-book example of drowned karst topography featuring a maze of limestone islets.

These have been shaped by sea water, gradually wearing away the lower part of the soluble coralline limestone creating overhangs that give the islands their classic mushroom-like form.

The Timolol sea cave which can only be accessed by shallow-draft canoe is a secret and sacred place known only to the villagers of Misool Island.

Its location is not marked on any map.

It is a giant, natural limestone cathedral the locals visit when their health is ailing paying their respects to departed ancestors, buried near the massive cave's entrance before praying for assistance.

Since the Islamic faith came to the region, followers make a point of visiting the cave before going on their pilgrimages to Mecca.

As sublime as this limestone cave is, it pales when compared to the wonder that lies beneath the sea.

With more corals than any other place on Earth, and possibly the greatest variety of fish swimming through its tropical waters, Raja Ampat is a globally recognized center of marine biodiversity.

There are over 1500 species of fish, nearly 700 species of mollusk and massive coral colonies that stretch well beyond the visible underwater horizon.

When scientists surveyed an area here the size of just two soccer fields they were amazed to discover a diversity of hard coral 10 times greater than that in the entire Caribbean sea!

At last count they have identified around 600 species of hard coral, 75% of all the known species on the planet.

There are spectacular plate corals here, massive brain corals, and a virtual underwater forest of gorgonian sea fans.

Sea fans are whole colonies of coral polyps living as one giant branching structure each polyp in a sea fan has eight tiny tentacles which reach out to grab nutrients that drift past in the currents.

Perhaps the most majestic creature living in the waters around the island of Missool is the gentle manta ray.

With wing spans in excess of three meters, they glide in from the deep ocean on the current hovering above the corals for a quick clean up by the smaller reef fish.

They get rid of any parasites that may have attached themselves to their skin and in return, the cleaner fish get a free feed.

Smart thinking from a highly intelligent creature, that just so happens to have the largest brain relative to its size of any fish species on the planet.

The waters of Raja Ampat act like a giant species factory pumping out larvae that is carried on powerful, deep sea currents which help to replenish other reefs, perhaps even as far away as Australia.

The currents that flow into Raja Ampat also bring nutrients with them and they form the foundation of the food-chain.

For local communities, this bounty represents their primary source of food and income so it's always been in their best interest to ensure its protection.

They are defined by, and depend on, the ocean that surrounds them and have their own system of managing and maintaining the resources at their disposal.

They still fish using poles and lines, rather than nets and free-dive for trochus shell which is still valued as a source of mother of pearl and used in jewelry.

Fishing is prohibited from a 1,000 square kilometer area that extends out from the island of Misool improving the biodiversity in the region, which attracts divers from all around the world boosting local employment opportunities and economic prosperity.

Pearl farms are becoming increasingly common too, in the larger, more protected bays of Raja Ampat and for them to function at all, the waterways need to be pristine.

So again, it's in everyone's best interests to look after the entire coastal ecosystem surrounding those farms.

By ensuring the environmental sustainability of any development that takes place here they ensure the future of generations to come.

(dramatic music) The world's largest coral reef system hugs the coast of Queensland, in north-eastern Australia.

It's the largest living structure on the planet made and maintained by the tiniest of creatures coral polyps, living together in complex colonies.

Some coral polyps are soft and flexible and more closely resemble plants.

Others produce limestone skeletons to support themselves and can easily be mistaken for rocks.

And it's these hard corals that act as building blocks for the wonder that is the Great Barrier Reef.

The dimensions of this iconic coastal marvel are staggering, stretching 2,300 kilometers it's visible from space.

It's roughly the same length as the west coast of America from Vancouver to the Mexican border, and the marine park that protects it, is approximately half the size of Texas.

Although it's called the Great Barrier Reef, as in a single entity, it's actually a massive marine ecosystem, made up of nearly 3,000 separate reefs that have formed between and around over a thousand magnificent islands.

Even some of the smaller coral cays such as Heron Island support an amazing array of life.

With no land-based predators, birds have the run of the place.

Buff-banded rails forage in the leaf litter, herons patrol the shorelines and no fewer than 75,000 black noddies nest in the island's trees.

The grand Pisonia tree has sticky seeds which can get on the birds' feathers, preventing them from being able to fly.

And if they can't fly they can't fish so they fall to the ground and die.

As the birds decompose, they provide nutrients to the plant that ultimately took their lives giving the tree an opportunity to grow new leaves for future generations of black noddies to use in the building of their nests.

Female turtles often nest directly beneath Heron Islands' trees, digging deep holes in the sand, before laying their large clutches of eggs.

There's no need for a turtle to hang around after covering her nest for the temperature of the sand is ideal for incubating her brood.

It's ironic that in the 1920s, Heron Island was best known for its turtle soup cannery.

Now it's famous for its research station, where scientists are constantly working to protect these gentle giants of the sea.

Six of the world's seven species of marine turtle live in the Great Barrier Reef waters but their future is becoming less certain.

As sea levels rise, their nesting sites are likely to flood drowning whole generations of turtles, even before they hatch.

As temperatures rise, even eggs that have managed to stay high and dry could be compromised cooking in the overly warm sand.

With so many scientists committed to understanding the problems associated with climate change and other stressors affecting the reef there is a glimmer of hope on the horizon.

A measure of confidence that this exquisite natural icon can and will remain one of the Seven Wonders of the World.

Inspiring us with its majesty, for many years to come.

We all have a stake in caring for the coastlines we share with so many other remarkable species.

For these extraordinary places will only stay natural wonders if we acknowledge that they are vulnerable and work together to protect them.

Ensuring we stay connected to nature and to events that changed the course of history.

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