- [Narrator] Oceans cover more than 70% of our planet.

This is where life on Earth began.

And where it continues to surprise those looking for animal encounters with bite.

Scientists are discovering new species every day here, on our shorelines, on our reefs, and out to sea.

These watery wonderlands are home to the largest, and indeed many of the smallest, creatures on Earth.

They harbor a Mardi Gras of diversity, a celebration of all things translucent, transformative, and transgender.

From the Great Barrier Reef in Australia, to the incomparable Galapagos Islands, marine animals are nature's supreme performers custom-built to provide a wealth of startling interactions and camera-ready for their close-up.

♪ Of all the creatures in the deep blue sea, the one that never fails to strike fear in the heart, is the great white shark, or white pointer.

Hollywood has made these animals infamous through fictional films such as "Jaws" and "Dark Tide."

But make no mistake, the premise behind these movies is real.

Great white sharks are natural born killers, lurking in the coastal surface waters of all the major oceans on Earth.

They prefer temperate waters but are often sighted in the tropics.

Two locations that are well known for great whites are South Africa and The Great Australian Bight off the coast of South Australia.

In both places, ocean currents carry water from Antarctica, laden with tiny organisms that form the basis of a complex web of life.

Plankton attracts fish, fish attract seals, seals attract the great white shark.

And the great white sharks, well, they attract people.

Cage diving with these charismatic creatures has become big business.

During seal breeding season, the supply of shark food is almost unlimited.

Despite their formidable appearance, great white sharks are not a huge threat to humans.

(gulls squawking) It is true about a hundred people a year are attacked by sharks and probably about half of those are made by great whites.

But most are not fatal.

Zoologists now know that these animals are naturally curious and most injuries to humans are just sample bites.

Great white sharks prefer to prey on sea lions, small-toothed whales, and sometimes other sharks.

They really are the ultimate hunters.

Shaped like torpedoes, they can tear through the water at 15 miles per hour.

Fully grown great white sharks have around 300 teeth arranged in several rows.

The ones at the front are knife-like, with serrated edges, intimidating and effective.

Fortunately the cages used on dives such as this protect those who seek the thrill of a close encounter without any associated risk.

The great white's sense of smell is no urban myth.

They can detect and home in on a small amount of blood from as far as five kilometers away.

Unlike most fish, these incredible sharks are warm blooded which is why they can maintain their body temperature in seas all over the world.

(diver shouting) Cage diving with great whites is the ultimate adrenaline rush, but the experience also allows scientists to increase their understanding of this remarkable species and its place on the blue planet.

Aquariums, which are slowly becoming as popular as zoos throughout the world, also afford opportunities for us to learn more about life underwater and to encounter less aggressive sharks in their admittedly somewhat controlled environment.

The size of the tanks clearly restricts the size of the creatures that feature in such exhibits.

So if you want to encounter the biggest fish in the sea, you'll need to return to the wild.

♪ Despite their name, whale sharks are not whales.

But it's obvious how the confusion has come about.

They are enormous, 20 times larger than the great white.

Fossils indicate this gargantuan fish may have been around for 250 million years.

It's a true dinosaur of the seas, but humans need not be alarmed.

The only prey on this giant's menu is microscopic.

Encounters with whale sharks are awe-inspiring to say the least.

And one of the most reliable places to see them, is here on Ningaloo Reef off the coast of Western Australia.

These gentle creatures swim to the surface to feed on tiny zooplankton, so it's easy to get relatively close to them just with a mask and snorkel.

Whale sharks gulp enormous quantities of water into their wide mouths, then filter out the plankton through a kind of sieve in their throats.

They do have teeth, 3,000 of them in fact, but they are barely six millimeters long and never used for eating.

Humans discovered whale sharks relatively recently.

The first recorded sighting was less than 200 years ago.

To better understand their migratory behavior and in so doing afford this species better protection from illegal fishing, scientists will occasionally fit an individual with a radio tracking device.

A relatively harmless procedure that is akin to having your ears pierced.

A less invasive tracking technique uses photo ID.

So anyone with an underwater camera can contribute simply by photographing the skin of any whale shark they encounter, for their spots are as unique as a human fingerprint.

Through this citizen science project, whale shark specialists have been able to determine the migratory patterns of individuals and better monitor the global population.

(air bubbles bubbling) Whale sharks cruise through Ningaloo every year between April and August, and they don't appear to be bothered by humans at all.

Ningaloo is one of the longest fringing coral reefs in the world.

It's a beautiful, wild place bathed in warm clear water.

The diversity of life here is bewildering.

Ningaloo lies at the point where the southern temperate waters meet the northern tropical currents of the Indian Ocean.

It's home to over 200 different corals and 500 species of fish.

♪ This pristine reef is a favorite hangout for another majestic giant, the manta ray.

Like all rays, these graceful mantas are a type of shark.

Growing to 5 1/2 meters wide, they are closely related to stingrays but thankfully, there's no nasty barb in their tails.

They do have teeth, but they're shaped like pebbles and not designed for biting prey.

Manta rays spend most of their time swimming in large vertical loops, sucking in plankton as they go.

Until recently, marine biologists believed mantas depended almost entirely on plankton.

But research now reveals manta rays only get about a quarter of their nutrition from this kind of surface feeding.

They catch the rest of it, mainly fish, hunting in the darker reaches of the ocean.

Tagged rays have been recorded swimming to depths below 400 meters and evidence is emerging that these impressive swimmers can dive down as far as a kilometer.

Celaphic lobes on either side of their mouths are actually pectoral fins adapted to help mantas funnel their food.

♪ Not all of the seas' creatures are famous for their propensity to kill or good looks.

Some are incredible to encounter simply because they're so bizarre.

Just off the coast of Whyalla in South Australia, there's a 10 kilometer stretch of rock on the seabed that well isn't particularly remarkable unless you happen to be here in winter.

This is the only time and place in the world for that matter, where you can reliably see huge numbers of giant Australian Cuttlefish.

With bodies, or mantels, around 1 1/2 foot long, they are the largest of their kind in the world.

Giant cuttlefish come here every winter to breed, because the seabed is a perfect platform for females to anchor their eggs.

In true rock star fashion, they live fast and die young, curling up their 10 tentacles, shortly after spawning.

Young cuttlefish take 12 to 18 months to reach maturity.

So they're only sexually active for a single season.

Their primary role is simply to live long enough to pass their flashy, over-confident genes to the next generation.

The jack-of-all performing trades, cuttlefish, have the underwater visual effects department well covered.

They can change color in an instant and work their way through a kaleidoscopic range of patterns.

They use these skills to help them with camouflage, or to signal alarm.

But during their mating ritual, it's all about showing off and upping your reproductive stakes.

Cuttlefish have been around for hundreds of millions of years.

Which begs the question, who is the real alien in this underwater encounter... the strange new creatures who seek to enter this world, or the cuttlefish they've come to admire?

♪ 1,000 kilometers off the coast of South America, there's a collection of volcanic islands that in their geographic isolation have developed habitats that have enabled many unique species to evolve.

(sea lion groaning) (water bubbling) On land, they appear to have little to fear from humans.

Indeed the reverse appears to be true.

These islands and their incredible collection of animals inspired Charles Darwin to write a book that changed the way we think about life on Earth forever.

They are, of course, the incomparable Galapagos.

There are 19 islands in the group in total, and they sit right on the Equator.

Their location is key to the strange and wonderful creatures that live here, particularly under the sea.

The Galapagos lie in a kind of triangle created by the meeting of three great ocean currents.

This has a dramatic effect on the weather, allowing a vast range of marine animals to wind up here.

The famous marine iguana is unique to the Galapagos Islands.

It's the only lizard that lives purely on algae and seaweed and swims underwater.

They're almost certainly descendants of the forest-dwelling iguanas of South America.

The theory is storms on the mainland may have set adrift rafts of sticks and debris, and a few unlucky land-based iguanas became stuck on board.

They were carried by the ocean current and dumped here, to begin a new life.

Over countless generations, they evolved the ability to survive by the sea.

Sharp teeth for scraping algae, a flattened tail for swimming and even a special gland which removes excess salt from their bloodstream.

♪ Birds also rule the Galapagos roost.

But two of the most striking seabirds are the frigate, with its extraordinary red throat pouch, and the blue-footed booby, easily identified by its outlandish blue feet.

The males are very proud of their blue suede shoes and show them off during mating dances.

The guy with the bluest feet usually gets the girl and the opportunity to pass on his genes.

The Galapagos Islands are also home to the world's only equatorial penguin.

They are a small but determined bird, ungainly on land, but absolutely amazing to witness underwater.

♪ One of the most joyous sights in the ocean can be found in almost all the warm waters of the world... dolphins.

At last count, scientists think we have 38 different species of marine dolphin, plus another five living in rivers.

Australia has 14 marine dolphin species and some of them are almost too easy to meet.

♪ Just offshore from the busy port city of Adelaide in South Australia, dolphins will go out of their way to initiate close encounters with humans.

The most common species here is the bottlenose dolphin.

These sociable animals live in pods, groups of around 12 individuals, that have developed a range of social skills to survive and support each other.

♪ Communication is key.

Dolphins use a complex combination of squeaks and clicks to talk to each other.

(dolphins squeaking and clicking) Their range of hearing is 10 times greater than humans, so they can pick up high-pitched sounds that we are unable to hear.

Dolphins usually hunt in a team, rounding up schools of fish, keeping them corralled until everyone has had an easy feed.

Most dolphins in large pods are female and not related to one another, although mothers will stay with their young for up to eight years.

(dolphins squeaking and clicking) ♪ Male dolphins form smaller pods of two or three, and they are thought to become friends for life.

They only approach the females when it's time to mate, which is often.

Dolphins can actually mate at any time of the year.

When a female gives birth, the others in her pod will help her, then go on to play a major role in protecting and rearing the offspring.

♪ Many marine parks and aquariums around the world offer opportunities to interact with dolphins.

They vie for attention with other equally endearing marine animals such as the beluga whale.

Calves are born gray, fading to white as they mature.

Adults are easily distinguishable by their rounded foreheads and lack of dorsal fin.

And they clearly enjoy an appreciative audience.

(people chattering) ♪ The Great Barrier Reef is a massive community of animals.

It comprises over 3,000 individual reef systems.

It runs along Australia's eastern coast from the Tropic of Capricorn north towards the Equator.

♪ The incredible variety of life here is hard to take in, the world's largest collection of corals, frequented by over 1,500 species of fish.

It's difficult to comprehend that a structure so large, it's even visible from space, begins with a tiny coral polyp, a soft bodied animal related to jellyfish and sea anemones.

A young polyp begins life drifting in the ocean.

When it lands in a suitable home, it attaches itself to the seabed, somewhere warm and shallow with lots of sunshine.

Then the miraculous process of reef-building begins.

These families of coral polyps have created a wonder of magical shapes and colors over many thousands of years.

And of course they provide a perfect home for the countless creatures living in the tropical seas.

The toxic stinging cells of the sea anemone are also an underwater oddity, for they provide protection for another small creature, the iconic clownfish.

This little fish would be easy prey for the larger predators on the reef.

So it's worked out a way to stay safe by living between the dangerous tentacles of a sea anemone.

So how does it avoid being stung and eaten like all the other fish unfortunate enough to swim this way?

The answer is by being very careful.

When a clownfish first arrives at a potential anemone home it performs a kind of dance, gently touching the anemone's tentacles.

This allows the fish to become accustomed to its stings.

Clownfish also develop a thick mucus on their skin which aids their protection.

Their ability to live where other fish fear to venture is astounding, but so too is their ability to change sex.

Clownfish are all born male.

Once a group is established, the largest will miraculously turn into a female, to ensure reproduction continues.

As the dominant individual in the group, she becomes capable of laying eggs for the males to fertilize.

If the female dies, then the largest remaining male will step up and change sex, to take her place.

It's quite easy to find clownfish on the Barrier Reef.

Most anemones have one hiding inside.

♪ When it comes to venom, one of the worst reputations belongs to one of the most beautiful fish on the reef, the lionfish.

Those elegant spines along its back, conceal a serious weapon.

Each spine runs down to a venom gland.

The venom contains a neuromuscular toxin which causes extreme pain, sweating, breathing problems, and even sometimes paralysis.

Lionfish are not aggressive.

Snorkelers and divers are unlikely to be deliberately stung.

Most injuries occur incidentally, when brushing past a fish or accidentally standing on one.

Lionfish are slow-moving and conspicuous, so it's just as well for them at least to have such a powerful defense system.

♪ The Great Barrier Reef really is like an enormous underwater city.

It provides shelter, food, and company for whole communities of extraordinary animals.

And one essential service that keeps the entire system healthy is provided at cleaning stations.

These stations are set up by a handful of unusual creatures, such as the aptly named cleaner shrimp... who survive by cleaning and eating dead cells and parasites from the skin of larger animals.

The local fish know where to go to get their teeth cleaned, and so do the local divers.

Cleaner shrimp are so confident, they will even crawl into the gill cavities and mouths of big fish, without any fear of being eaten.

Scientists have recently discovered how crucial cleaning stations are to the reef.

In sample areas where cleaner fish were removed, 3/4 of the fish population disappeared.

It's assumed that many reef creatures would quickly succumb to disease and ill health if they were not regularly cleaned.

So it's no wonder these are popular places.

The number of visitors at any one cleaning station could be well over 2,000 per day.

And with up to 1,200 parasites being removed in a single fish cleaning session, it's a wonder these tiny shrimp can keep up with the demand.

♪ The Great Barrier Reef is perhaps best known for its profusion of small, colorful fish.

Great schools of anthias catch the sun in shades of peach and gold.

Exotically named individuals like angelfish, sweetlip, and damselfish swim gracefully through the branching corals.

The reef also provides a home for strange creatures like barrel sponges and giant clams.

Many of the islands that rise from the reef are fringed by idyllic, icing-sugar-like beaches created by a creature in the sea, the bumphead parrotfish.

This is the world's largest parrotfish, and its favorite food is coral.

It uses the massive bump on its head to knock off big chunks of coral and its beak-like mouth to crush and consume the spoils.

The fish is actually only interested in the polyps and algae inside the coral, but to get that takes a bit of work.

The crushed coral skeleton is then excreted as waste.

Waste that washes up onto atolls such as this as sand.

Yes, that deliciously soft powder beneath your toes is mostly made from parrotfish poo.

Studies in the Maldives have shown that 85% of the sand there has come from the rear end of parrotfish.

One type of fish that's well designed for living in inaccessible places on the reef, is the moray eel.

♪ These impressive fish can grow to three meters long and be as thick as a human waist.

Despite these intimidating dimensions, moray eels are not aggressive to humans.

Divers can come across morays in tropical and temperate waters around the globe, but Northern Australia has 15 different species of this spectacular eel.

It takes about 20 years for these eels to reach their full size.

As this time approaches, many of them turn into females.

Within a month of mating however, they will lay their eggs and die.

One remarkable species of eel was only discovered when scuba diving became popular.

These eels live out on the open sand so they've developed a unique method of remaining inconspicuous, despite their obvious exposure.

They simply pretend they're a field of seagrass.

Spotted garden eels live in huge colonies on sunlit patches of the sea floor.

Their range extends across the Indian Ocean to Africa and up the Western Pacific to Japan.

To feed, they rise out of their burrows and sway in the ocean currents, taking in zooplankton as they go.

If alarmed, the eels instantly retreat into the seabed and the sand appears as if no one was ever here.

♪ The world's oceans are home to seven marine turtle species.

One of the largest, the loggerhead, can tolerate the colder oceans of Northern Europe and the South Atlantic.

They can be found anywhere except the extreme conditions of the North and South Pole.

They prefer coastal areas but are often spotted traveling way out to sea.

Hawksbill turtles avoid deep waters and are usually found in the warm seas near coral reefs where their favorite food, sponges, grows in large numbers.

Their dramatic serrated shell and bird-like beak makes them easy to identify.

The gentle green turtle is the most prolific and widespread.

They live in and around the tropics, including Hawaii.

♪ Green turtles are not alarmed by divers, so it's often possible to swim right up to them to get a really close encounter.

All marine turtles begin life in an egg buried in the sand.

Their mothers make the laborious journey up the beach to dig a nest.

Once she begins laying, she enters a trance-like state, where nothing, not even onlookers, will disrupt the job at hand.

One to 200 eggs later, depending on the species, Mum covers the pit completely, then returns back to the sea.

In the course of a season, a female green turtle may do this five or six times.

Set and forget.

And if all goes according to plan... six to eight weeks later, newly hatched turtles will begin to emerge.

♪ As they make their way to the ocean, they run a veritable gauntlet, hoping to avoid predation by crabs hiding below the sand and birds wheeling overhead.

Once they enter the water, it's game on, for hordes of hungry fish and ravenous sharks are patrolling the shallows.

The odds of surviving are stacked against the hatchlings.

Fewer than one in a thousand survive.

But if this little turtle can make it through the breakers and out to the open sea, its chances of surviving to adulthood are good.

The years between hatching and reaching maturity are known as the lost years, for scientists are still trying to work out where they go.

One thing's for certain, however.

They have an inbuilt natural GPS that will guide them back to the same area where they were born, when they are ready to breed themselves.

Turtle populations around the world have taken a hammering over the years.

They're regularly killed in discarded nets that drift silently through the sea or starve to death after mistaking plastic shopping bags for jellyfish.

Adding to their 21st century woes, climate change.

For the time being however, turtles are still with us.

And encountering these ancient mariners in the ocean remains an inspirational, uplifting experience.

♪ The island of Eil Malk in the Pacific nation of Palau, is both beautiful and remote.

And it affords one of the most ethereal animal encounters on Earth.

The lifeforms that have developed here are truly mesmerizing, golden jellyfish.

The reason people can safely swim here is that the jellyfish are not able to sting.

Although the lake is saline, these jellyfish have been cut off from the sea for over 10,000 years.

No open sea means no predators.

And no predators means no need for defenses.

These jellyfish have well and truly let their guard down and have gradually lost their ability to sting.

The lake was formed when global sea levels rose after the last ice age.

It's still connected to the neighboring lagoon by three tunnels, so water washes in here with every high tide.

Around eight million jellyfish live here when conditions are optimal.

At last count there were only about 600,000.

But that's still a heck of a lot of jellyfish to contend with.

No one knows exactly why, but rainfall here is the lowest it's been in 65 years.

As a result, the lake salinity levels are the highest on record.

It's too early for scientists to tell whether the reduced jellyfish numbers are a natural fluctuation or a result of climate change.

The last population crash was in the 1990s after an El Nino event, and the good news is the jellyfish bounced back.

Everyone here in Palau is hopeful the same thing will happen again.

♪ Of all the animal encounters possible in the marine environment, this one never fails to delight causing many to spontaneously laugh out loud underwater.

♪ Australian sea lions may be one of the rarest species in the ocean, but these adolescent pups don't seem too concerned at all.

They just want to play.

These sublime animals live just off a remote beach on the Great Australian Bight, called Baird Bay.

The water can be cold, but if you're prepared to brave it, the welcome you'll receive is very warm indeed.

There are only three rules to enjoying an encounter without upsetting the balance of nature: no sunscreen, no touching, and no chasing.

Sea lions differ from seals in two big ways.

They have external ear flaps, and they can walk on their back flippers using their front ones to prop them upright.

There are only about 12,000 Australian sea lions left in the world, but the local population here at Baird Bay is thriving.

Since legislation has ensured their protection, numbers have increased threefold.

♪ Another spot in the southern oceans famous for its marine mammals, lies on the other side of the Tasman Sea in New Zealand.

Its standout feature, apart from the sheer beauty of the place above the waterline, is a gaping canyon, just offshore, and it's a daunting three kilometers deep.

Kaikoura is a former whaling station north of Christchurch on the south island of New Zealand.

The name means crayfish food in the local Maori language, and that provides a clue to the unusual abundance of sea life found here.

The immense underwater canyon below these waves is rich with krill and other plankton.

This in turn draws other sea animals all the way up the food chain.

Some of the noisiest come here to breed, fur seals.

One male commands a harem of about 40 females and he'll make a serious song and dance about keeping them for himself.

It's a hard life for a female fur seal.

They give birth and almost immediately fall pregnant again.

And year after year, they return to Kaikoura to repeat the cycle.

(sea lion howling) ♪ Of equal interest to animal lovers is the sperm whale, the animal with the largest brain of any creature known to have lived.

Its tail fluke is over four meters across, driving these enormous animals along at nearly 40 kilometers per hour.

This is one of the few places in the world where sperm whales can be seen so close to shore.

(lively music) If size really matters when it comes to animal encounters, then you really can't overlook the blue whale, the largest animal in the ocean.

In fact, it's the largest animal that has ever lived.

There are two world-renowned places for seeing them.

One is the Monterey Canyon off the coast of California in the U.S.A.

The other is the east coast of Australia.

Between May and November, these iconic animals migrate along the coastline.

They're traveling from the rich food sources in the Antarctic to warmer waters for breeding.

To see one in the wild is an unforgettable experience, even from the air.

Fully grown blue whales are roughly 30 meters long.

Their heart alone is as big as a car, and yet they feed exclusively on krill, tiny shrimp-like organisms that have a colossal significance in the sea, forming the basis for many marine food webs.

Apart from being the biggest animals on the planet, blue whales are also one of the loudest.

They communicate using low groans, grunts, and pulsing sounds, and they can hear each other from 1,600 kilometers away.

♪ Humpback whales are a far easier species to encounter in the wild, in glorious places, such as this.

The Inside Passage is a well-known coastal route that weaves its way through the islands on the Pacific Coast of North America.

Humpbacks will outperform just about any other whale species in the ocean and are regularly seen waving their fins as if to attract attention or breaching clean out of the sea.

They are a migratory species and travel further than most, feeding in Antarctica in the summer months, before heading to warmer climes to breed.

They are thought to live up to 50 years and the age of a whale can be measured in much the same way foresters are able to age trees.

When scientists discover a dead whale, they remove the waxy plugs from its ears and simply count the number of rings.

The kingdom of Tonga, a collection of 170 islands lying right in the middle of the vast Pacific Ocean, offers an even closer encounter with whales.

Hundreds of humpbacks choose to come here every year to raise their young.

From July through to November, the humpback females stay here to give birth and nurture their calves.

The females fast while they're nursing young, who greedily consume up to 600 liters of thick, rich milk a day.

And they don't seem to be bothered by humans dropping in for a visit.

It's a truly magical marine experience.

Mothers and their young swim close together, often touching each other with their flippers as a sign of affection.

It will take 10 years for these calves to be fully grown and they will stay close to their mothers for much of this time.

♪ It is clear we humans pose less of a threat to animals underwater than we do above it.

We swim slowly, and of course, we can't stay forever in their ocean realm.

We would appear to be a curiosity rather than a threat to marine animals.

So they often allow us to get much closer to them than land animals do.

And that, in essence, is what makes marine encounters some of the most spectacular wildlife experiences of all.

♪