Magical Land of Oz

As the dawn breaks across Australia,

the marsupials go to bed.

Except for the ones that don't.

Because there are exceptions to every rule

in this land of wonders.

And magic does not have rules.

It has dragons...

miniature dancers...

spiky egg layers.

But the land is only where the wild things begin.

The seas surrounding the island hold even more wonders.

Three different oceans circle Australia -

the cold Southern Ocean,

the calm sanctuary of the Pacific with its reefs and islands,

the warm Indian Ocean supporting schools of awe-inspiring predators.

Together, the three oceans create a rich mix of marine diversity

and an explosion of life

in the magical land of Oz.

Australia's ocean wilderness

is one of the most extraordinary places on Earth.

It is both beautiful and bountiful.

It starts with the tiniest fish...

which, in turn,

support an astonishing array of larger creatures.

Dusky sharks are fast, streamlined predators

that can grow over four metres in length.

Dense schools of sardines on this Western Australian coastline

attract their hungry mouths.

The fish are fast

and their quick shimmering changes in direction

make it hard for the predators to pick out an individual.

Their prey are herded towards the shallows.

In the shallows, there's also a group of young board riders.

Confident that the sharks are keeping themselves busy,

the swimmers have entered the fray for a close encounter.

There are 375 shark species in the world,

yet only three are responsible for most human attacks.

Dusky sharks are not amongst them.

More and more sharks join the feast,

drawn from far and wide.

From higher up, the sheer size of the scene becomes clear.

They have become one colossal bait ball.

A seething mass of predators and prey spreads along the coast,

in a scale rarely seen anywhere else on the planet.

The abundance of fish still teeming in Australia's oceans

supports many marine predators.

But not all of them remain underwater.

Just over 60 kilometres off South Australia

lies Pearson Island.

Often compared to the Galapagos,

this archipelago has a precious cargo of species

found nowhere else on earth.

The Australian sea lion is amongst the rarest of its kind in the world.

Its population reached dangerously low levels

after being hunted for close on two centuries.

The world's least polluted and best stocked waterways

have helped sea lions back from the brink of extinction.

These are ideal fishing grounds for a sea lion mum.

The island's small sandy bay

provides the perfect nursery for her pups.

He's not confident enough

to follow his mother into the waves just yet.

Alone, he watches the more experienced youngsters

mess about in the water.

Perhaps someone close to his own age will provide some company.

But mothers can be protective...

..and fathers horribly hostile.

The colony can be a dangerous place to wander in search of a playmate.

Mothers come ashore and reunite with their pups for a feed.

But his wait continues.

In Pearson Island's toddlers' pool,

the young pup has finally found a friend...

..from a different species...

..a long-nosed fur seal pup.

These rock pools at the back of the bay

provide the perfect playground.

As the pup's hunger grows, he watches for his mother's return.

Sea lions are some of nature's greatest ocean acrobats.

So simply coming ashore should be easy.

She needs to pick a landing spot.

But the crashing waves are making it hard.

If she's not going to clear a wave in time,

she needs to abandon the plan for a wiser one.

The sandy beach is surely an easier landing site.

As fast as his flippers can carry him, the pup runs to his mum...

..and finally gets his milk.

He will rely on his mother for 18 months

before he must catch his own dinner, like the older sea lions.

One of the reasons sea lions can thrive

in the seas around southern Australia

is the abundance of prey.

And now, in winter,

one of their favourite foods is starting to mass

in one of the most intriguing and graceful animal congregations,

known only in these waters.

In the wide shallows of Spencer Gulf on Australia's south coast,

as the water temperature drops below 12 degrees in winter,

a magical phenomenon takes place.

Giant cuttlefish, up to a metre in length,

are found only in Australia.

Masters of disguise,

they can change the colour and texture of their skin

to blend with their surroundings.

At this time of year, though,

it's all about standing out from the crowd.

This patch of reef, just over a square kilometre in size,

has been inundated with thousands of courting cuttles.

With a ration of 11 males to every female,

not every male is going to get lucky.

This female has accepted the protection of a larger male.

But now he must hold on to his mating rights

in the face of constant challenges from eager rivals.

The males quite literally size each other up.

By splaying out his tentacles,

turning white and angling his body at 45 degrees,

this alpha male attempts to appear larger than his challenger.

The female is hidden below

while waves of black add to his display of strength.

As rivals converge on either side,

it's almost impossible to keep his mate concealed.

While the alpha male is distracted,

his mate drifts from cover.

A smaller male sees an opportunity and moves in.

The interloper drags her as far as he can,

before forcing her into his twisted embrace.

But the larger alpha male is quick to reclaim his prize.

Like a fire hose,

he flushes out the sperm of previous copulators.

As the last to mate, he will be the one to fertilise her eggs.

The pair can finally get down to the business

of finding a place to nest.

Any prospective home for their eggs requires close inspection.

Satisfied, she begins depositing their first clutch.

It takes around six minutes before she can lay another egg.

So the male must guard her closely.

It's a prime nesting place, coveted by other cuttles,

who feel their way closer to the crevice and the fertile female.

One by one, the delicate eggs are fixed.

To stop others entering the cave,

he flattens his body,

making him appear even larger,

doing his utmost to impersonate a monstrous kraken.

Males venture closer, testing his resolve.

His fatherhood is on the line.

It's a warning sign -

stay away from this monster's lair!

Despite the show of brute strength,

challengers persist.

The monster allows them even closer,

until...

Cuttlefish expel ink to confuse predators.

But this is a desperate attempt

to escape the clutches of one of their own...

..the largest male on the reef.

This unique marine spectacle was on the verge of being lost.

In a single season,

commercial fishermen caught 240 tonnes of cuttlefish

at this breeding site,

before a fishing ban was put in place.

Today, these calm inshore shallows

allow this amorous gathering to continue in relative peace,

while further out to sea,

storms are brewing.

In the depths of winter, polar winds from Antarctica

whip up huge swells across the Southern Ocean.

This is the ocean's engine room,

generating waves that will roll across the planet.

And Australia's southern coastline is shaped by this powerful force.

As the ocean swell nears the outer fringes of Australia,

huge waves, as high as seven-storey buildings,

have been recorded off Tasmania.

In winter, many of the ocean wanderers

leave this violent sea scape...

..to seek refuge in the Great Australian Bight.

The arid Nullarbor plain reaches a dramatic end,

as land plummets to the ocean, 150 metres below.

Every year in winter,

Southern Right whales gather in these cliff-side coves.

This female left her feeding ground in the Antarctic,

and travelled over 4,000 kilometres to give birth.

The warmer water is gentle on her newborn,

yet to grow its insulating blubber.

She will nurse her calf here

until it's strong enough to face the long migration south

at the start of spring.

But it's not all gentle play

for whales in these waters.

These cliff-side coves are the arena

for spectacular mating events.

At nearly 15 metres and each weighing as much as 100 tonnes,

four males close in on the lone female.

Dolphins become curious onlookers.

Females are known to go belly-up

in an attempt to keep their genitals away from males,

as they wield their supersized anatomy.

Almost four metres long,

the penis of the whale delivers a gallon of sperm during mating.

Unlike the Southern Right whales,

this dolphin pod remains by the coast throughout the year.

And despite the size difference,