♪♪ NARRATOR: In the middle of the Pacific Ocean, the world's most isolated island chain is shark paradise.

Some hunt in gangs, others ride the tides to find food.

The biggest are loners.

But no matter what their size... ...or what they eat... ...Hawaii has everything sharks need.

♪♪ Shallow reefs here are packed with fish.

♪♪ The deeper blue offers different fare.

The warm water calls to many.

If it seems too perfect, it just might be... for now.

The biggest sharks with the biggest needs may be moving here, too.

♪♪ ♪♪ ♪♪ NARRATOR: These humpback whales are finally home.

After feeding all summer in the Gulf of Alaska, they've traveled over 3,000 miles to return to Hawaii, where they were born.

♪♪ Some females have journeyed to these warm, clear waters to entertain a mate or two.

And soon, those that are pregnant will give birth to their own calves here.

♪♪ The new mothers will be extremely protective of their newborns.

They have to be.

Because while this place looks idyllic, the whales have come back to an age-old battleground.

♪♪ Tiger sharks are the apex predators in Hawaiian waters, 15 feet of clever camouflage constantly patrolling the channels between islands.

They prey on whale calves, a feast they've been anticipating all year.

♪♪ Then, these mighty opponents will come face-to-face, 2,400 miles from the nearest continent.

♪♪ Hawaii's archipelago is the most remote on Earth.

The eight main islands are merely the summits of a vast, submarine mountain chain stretching 1,500 miles across the Pacific.

♪♪ They're all the result of a deep-sea volcanic hot spot that builds new islands when the tectonic plates above it move.

♪♪ Kilauea, on the Big Island, is the most active volcano on Earth.

It's been continuously erupting for the past 40 years.

♪♪ ♪♪ Lava meanders down the slopes in molten paths to the sea.

♪♪ ♪♪ These islands are primeval, but in Earth's geologic timeline, Hawaii is a newcomer.

The first island rose above the sea a mere 5 million years ago.

And, in the middle of nowhere, it became an anchor for coral spawn drifting in from open water.

♪♪ ♪♪ Hawaii became a magnet for life, sheltering thousands of unique species found nowhere else in the world.

Hawaiian monk seals and Hawaiian octopuses are natives here.

♪♪ But Tiger sharks are much older than Hawaii.

They somehow discovered these islands in the course of their migrations.

These days, Hawaii's bays and inlets offer year-round opportunities for every palate.

Both the massive and the miniature enjoy the islands' embarrassment of undersea riches... ♪♪ ...including at least 40 species of sharks... ♪♪ ...and their cousins, the rays.

♪♪ The volcanoes created stark basaltic plains underwater, which were first colonized by algae and then by tiny coral polyps.

Over time, life moved in, creating a stationary buffet for carnivorous sharks, eels, tangs, and angelfishes, just to name a few.

At least 25% of Hawaii's coral reef fishes are native and only live here.

It seems impossible that this delicate fairyland could spring from such violent brimstone and fire.

Hawaii's two active volcanoes are the modern agents of a process that is still unfolding.

Kilauea and Mauna Loa are both on the Big Island -- also called Hawaii -- which is the youngest island in the chain.

When super-heated magma meets the cool ocean, a cauldron is born.

As the lava cools, trapped air forms an undersea labyrinth of tunnels and tubes, creating superb miniature bunkers for those that need sanctuary.

They draw travelers in from the open ocean.

♪♪ And even sharks need to find a safe haven.

♪♪ The lava tubes are a perfect retreat for nocturnal whitetip reef sharks.

♪♪ Slender whitetips often escape into the narrow passageways, thwarting more massive pursuers.

♪♪ ♪♪ These reef dwellers sometimes become tiger shark prey because they're so much smaller.

At five feet long, they're right in the middle of a tiger shark's menu.

This tiger cruises just outside the maze, perhaps hoping to surprise a whitetip away from home.

♪♪ Deep in their lairs, whitetips can relax.

They use specialized muscles to draw in oxygen-rich water over their gills, making them one of the few shark species that doesn't need to swim in order to breathe.

They cruise through the murky lava jungle, always searching for a better place to rest.

Though they're able to suspend activity in parts of their brain, they never actually sleep.

They spend hours like this, simply resting, sometimes alone, sometimes together.

♪♪ Light doesn't reach into most of the lava maze, but nocturnal whitetips still wait for the dark of night to venture out.

♪♪ Carefully, cautiously, they'll morph from the hunted into the hunters... ...searching their small territories for prey that's also active at night.

♪♪ ♪♪ The reef during the day is a different world, whether you're predator or prey.

♪♪ Beyond the coral heads, in open water, there's no place to hide.

♪♪ This silver flash is actually a school of small mackerel called akule.

As juveniles, they lived on the reef, but as adults, they've moved into deeper water.

They gather in the tens of thousands, seeking safety in numbers.

♪♪ When they sense danger, the small fish react by crowding close together in what's known as a bait ball.

♪♪ ♪♪ Instead of seeing individuals, predators confront a much larger, confusing "creature."

♪♪ But sometimes increasing their profile only attracts more lethal attention.

♪♪ Bluefin trevallies, 3 feet in length, are some of Hawaii's most efficient carnivores.

♪♪ Aggressive and sleek, they can carve up a bait ball with exquisite precision.

♪♪ Akule caught in the rift are the first to be devoured.

The others try to flee.

♪♪ ♪♪ The sounds of plunder draw gray reef sharks to the scene.

♪♪ Then, an elegant silky comes in from the blue.

They have the ability to hear prey through open water.

♪♪ Now, the Akule have drawn multiple sharks to the nearshore reef.

Sharks may hunt cooperatively, but it's every individual for itself when it comes to food.

♪♪ ♪♪ The hunters try to corral the baitfish into more manageable masses.

♪♪ ♪♪ After enduring attack after attack... the Akule are tiring... ...but it won't be over until the sharks are satiated.

♪♪ In the end, bottom dwellers reap the last spoils of war.

A blue pincher crab is camouflaged by algae covering its claws... ♪♪ ...allowing it to steal a prize, almost.

Like a furtive ribbon, this undulated moray eel has followed the scent of flesh.

♪♪ Needle-like teeth shred the meal.

♪♪ Surviving Akule disperse with their casualty count unknown.

♪♪ Back on the reef, there is a constant kaleidoscope of color and danger.

♪♪ Every creature here has evolved a strategy to meet its needs.

The sharks are no exception.

♪♪ Blacktip reef sharks are Hawaii's homebodies.

♪♪ They prefer shallow water, which suits their docile, social nature.

They often convene in groups.

♪♪ Around the Big Island, these small sharks use the tides in order to hunt ever closer to shore, the best place to find tasty crustacean prey.

♪♪ And the tides always deliver.

♪♪ The Big Island is also known for its black sand beaches, formed by volcanic glass that's rich in iron.

But, it's not the color of the sand that attracts green sea turtles to Hawaii.

This is the natal home of the largest hard-shelled sea turtles in the world.

♪♪ Adults sport shells more than four feet across and can weigh over 300 pounds.

As juveniles, their diet is quite eclectic, but adults graze on algae and sea grass, which tints their internal fat a pale shade of green.

Female sea turtles of all species come ashore in order to lay their eggs.

[ Moans ] But, this is the only place in the world where males haul out alongside females.

No one knows why.

The males don't guard the eggs and the turtles don't mate here.

This exceptional behavior is a complete mystery.

♪♪ Oceanic nomads, green sea turtles swim endlessly until they reach maturity, somewhere between 20 and 50 years.

Scientists don't know how long these prodigious seafarers live, but they suspect it's more than a century.

♪♪ Cruising through clouds of plankton for decades allows algae and barnacles to grow on the platforms of their broad shells.

♪♪ This provides great benefits for the barnacles.

But, as they accumulate, ferrying such a load can slow turtles down.

♪♪ The barnacles attach themselves with organic cement.

They're permanent passengers.

Unless knocked off in the tussle of turtle sex.

♪♪ But there is a way to limit their growth -- with a little help from some friends.

♪♪ ♪♪ These brown and yellow tangs can digest tough marine algae that grows along with the barnacles.

♪♪ This helps the turtles by keeping their shells smooth, making it more difficult for new barnacle larvae to attach.

♪♪ On Hawaii's reefs, sea turtles aren't the only customers to benefit from a good cleaning.

♪♪ But it's more of a challenge for grey reef sharks to take advantage of the tangs because they must keep swimming, in order to breathe.

♪♪ They solve the problem by adopting a vertical stance, with snout and gills facing into the oxygen-rich current.

♪♪ ♪♪ ♪♪ Cleaner fish don't fear their shark patrons because the symbiotic relationship provides relief from parasites for the predators.

Both creatures benefit from the alliance.

♪♪ Cleaner wrasse even follow their customers in order to clean -- and eat -- mucus from gills, noses, and teeth.

♪♪ ♪♪ But this remarkable upright dance is a lot more taxing for the little fish.

♪♪ These humble janitors ensure the health of many species, which makes them one of the most important fish on the reef.

♪♪ Like all urban places, the reef is a bustling place.

But, beyond Hawaii's coral cities, the rural seascape becomes stark, desert-like.

It appears almost devoid of life and, yet, there is prey here, which an alien-looking hammerhead has just the tools to detect.

♪♪ The bizarre shape of its head makes for an imposing silhouette... ♪♪ ...and enables those strange, wide-set eyes to see a near 360° view of its hunting grounds.

♪♪ Like all sharks, hammerheads use special sensors to detect the bioelectrical fields of creatures around them, but these peculiar beasts have twice as many as other sharks.

It's as though they were especially designed for this stark hunting ground.

♪♪ The hammerhead is scanning for signals from its favorite prey.

♪♪ But, stingrays are experts at hiding and escaping in this sandy expanse, so the hunt continues.

♪♪ Off the island of Oahu, there's another desolate expanse.

But this is an undersea prairie, with its own waving strands of garden eels.

♪♪ These native Hawaiians are desperately shy... ♪♪ ...partially emerging from their burrows only to devour zooplankton.

Hundreds plant themselves where strong currents deliver food to their doors.

This species is only found in Hawaiian waters.

♪♪ Each will spend its entire lifetime in the exact same spot.

♪♪ The eels' large eyes spot this roving tiger shark.

♪♪ But any intruder will trigger the group to disappear back into their sandy dens.

♪♪ ♪♪ The only creatures garden eels need to fear are each other because males engage in brutal territorial fights.

♪♪ The tiger shark has no interest in the slender stalks below.

♪♪ It's headed some 500 miles northwest, for a proper meal.

♪♪ ♪♪ The tiger's destination is an eerie spit of sand in the middle of nowhere, once a military airstrip during the Second World War.

[ Birds squawking ] Today, the only residents are birds, monk seals, and, occasionally, green sea turtles.

Tern Island is part of the Hawaiian Islands National Wildlife Refuge and it's a critical sanctuary for millions of nesting seabirds and thousands of wintering shorebirds.

It's also a magnet for a maverick group of tiger sharks searching for seal prey.

♪♪ Aside from a bat, the Hawaiian monk seal is the only mammal endemic to the islands and there are only about 1,500 of them left.

♪♪ [ Snores ] ♪♪ Many show signs of lucky escapes from shark jaws.

♪♪ ♪♪ Tigers will also take turtles, and even dolphins.

[ Whistling ] ♪♪ These hunters have liberal tastes in prey.

Anything and everything is on their menu and this far-flung outpost of Hawaii offers them something unique.

[ Chirping ] Laysan albatross parents leave the island before their chicks' transition from landlubbers to open ocean voyagers.

[ Squawking ] Designed to glide over an endless expanse, extra-long wings make learning to use them extra challenging.

Black-footed albatrosses are here, too.

Like the Laysans, they lay just one egg every other year.

The Northern Hawaiian Islands host 90% of the breeding albatrosses in the world.

From terns to frigate birds, albatrosses to gannets, 18 species rely on this tiny spit of land.

It's an essential mid-ocean nursery for half a million seabirds.

Once they become one with their wings, the chicks' maiden voyage will be all the way to the Bering Sea.

♪♪ But, first, they must make a successful flight.

♪♪ It's harder for them to succeed than for most birds because of the strength they must build to power such long wings.

♪♪ ♪♪ ♪♪ The small group of tiger sharks around Tern Island knows when -- and where -- chicks practice takeoffs.

♪♪ And the chicks, focused on flight, have no idea of what lurks beneath the waves.

♪♪ Most fledglings become airborne after a few attempts.

♪♪ But not all.

♪♪ In other places, a water landing would just be part of the learning process, a gentle respite for the beginner attempting to get the hang of takeoff.

♪♪ But here, soggy and exhausted, the chick's a sitting duck.

♪♪ ♪♪ In order to escape the predator's jaws, the chick attempts to walk on water.

♪♪ But, there's no miracle today.

♪♪ ♪♪ ♪♪ ♪♪ This chick's first flight was also its last.

♪♪ It's impossible to know if the other young birds realize what they've just seen.

♪♪ Once they leave the rookery on Tern Island, they won't be back for three years.

Then, they'll choose their mate for life and hatch chicks of their own.

The tiger sharks will be waiting.

It's a strange twist in the story, for the chicks that escape the sharks will prey on fish in return.

♪♪ The Hawaiian Sun sinks swiftly below the horizon.

Here, in the tropics, twilight is brief, a mere moment of magic.

♪♪ ♪♪ On the reef, creatures are already preparing for their nightly business.

♪♪ It's dinnertime and miniature lanterns are about to appear as guides to a feast.

♪♪ Tiny fish and tasty zooplankton rise from the deep, flaunting their bioluminescence.

♪♪ These animals use chemical reactions within their own bodies to make light.

They might become instant prey, serving as the first course in a complex food chain.

♪♪ Some use their inner glow to draw even tinier prey closer.

♪♪ Still others shine to attract mates.

♪♪ ♪♪ Box jellyfish aren't impressed by the displays.

To them, the radiant organisms are simply...food.

♪♪ The light show attracts more plankton and, ultimately, giants from the deep.

♪♪ Giant manta rays are shark cousins, but they are filter feeders, with wingspans that can reach 29 feet.

♪♪ At birth, mantas are rolled up like burritos and then unfurl to an astonishing six feet.

♪♪ But no two are alike.

Blotches on their underbellies are equivalent to human fingerprints.

They're thought to have individual personalities, too -- some curious, others shy -- which researchers consider a sign of intelligence.

♪♪ They're all voracious.

♪♪ Sophisticated fins, called devil horns, whisk plankton into their cavernous mouths.

♪♪ But, it's recently been discovered that those gaping mouths are also swallowing great mouthfuls of small fish, whole.

♪♪ ♪♪ They sweep the night ocean until dawn, near Kona on the Big Island.

♪♪ Graceful, gentle giants, these marine marvels have only large sharks to fear.

♪♪ Ironically, the largest shark of all is also benign.

♪♪ Whale sharks are the largest sharks on Earth and sometimes they pass through the Hawaiian Islands.

Slowly.

♪♪ They swim extreme distances because they need enormous amounts of plankton and coral spawn to power their bulk -- up to 90 pounds per day.

♪♪ ♪♪ Forty feet long, their mouths stretch four feet wide.

But plankton is strained and swallowed by a throat so small, it's just the size of a coin.

♪♪ Thick, rubbery skin acts like armor to deter would-be shark predators, but not a bevy of freeloaders.

♪♪ Remoras accompany whale sharks everywhere they go and position themselves to ensure they don't miss any scraps.

♪♪ ♪♪ ♪♪ There are more giants here.

Nine thousand pilot whales are Hawaiian residents.

[ Squeaking ] They're actually supersized dolphins, cruising the deep channels between islands, capable of diving 3,000 feet down in search of squid.

Large, fatty melons on their foreheads magnify the sounds that they use to communicate and to find prey through echolocation.

[ Clicking ] They travel in large groups, made up of several families.

Sharks don't target these intelligent, 20-foot-long mammals, but some follow them.

Oceanic whitetips rely on the whales' sonar to lead them to food in the open ocean and the pod doesn't seem to mind.

The sharks grab fish scraps when the pilot whales pillage a school.

In this realm of endless blue, it's a challenge for them to get enough to eat.

So, every meal counts, including ones the whales have already digested.

In other places around the world, sandbar sharks migrate long distances, but Hawaii has everything they need, so they live here year-round.

They prefer to stay deep.

It's unusual to see them so close to the surface.

They're just finishing a meal of tasty mackerel, known in Hawaii as opelu.

The sandbars have formed a gang, probably all males, because females travel alone.

They've had the school of opelu to themselves for quite some time.

Then, a massive bronze whaler decides to make an appearance to the party.

♪♪ Little is known about these sharks, but they tend to return to the same locations over time.

♪♪ Today, there's not much left for the latecomer.

♪♪ ♪♪ ♪♪ Meanwhile, off the coast of Maui, a tiger shark is on patrol.

♪♪ Tigers in Hawaii have been waiting for this season.

♪♪ By now, many humpback calves have been born.

♪♪ They'll nurse for at least a year, growing a foot every month by drinking 100 gallons of rich milk every day.

♪♪ Mother whales will try to keep their newborns close, but tigers are clever and stealthy.

♪♪ And, while adult whales can submerge for close to an hour... ♪♪ ...little calves must surface every few minutes to breathe.

♪♪ This is when they are most in danger.

♪♪ Many survivors show terrible scars from shark attacks.

♪♪ In just a few months, they'll be too large for the sharks to even consider.

♪♪ But, until then, the tigers will actively hunt them.

♪♪ ♪♪ When the predator sees an opportunity, it moves in for the kill.

♪♪ Still, even newborn calves are roughly the same size as tiger sharks, and a challenge.

♪♪ Today, this one escapes a gruesome fate.

♪♪ Hundreds of humpback calves are born in Hawaii every winter and not all will be so lucky.

♪♪ Those that escape the fearsome jaws will migrate north with their pod.

♪♪ ♪♪ Foiled for now, the tiger shark smells the equivalent of an underwater dinner bell.

♪♪ It's ringing 80 miles away, along the coast of the Big Island, announcing a dead sperm whale still afloat offshore.

♪♪ One hundred thousand pounds of nutritious flesh won't go to waste.

♪♪ We don't know how, or why, it died, but internal gases have kept the carcass from sinking into the abyss.

♪♪ Blubber is a calorie bomb and nature has dropped it into shark-filled waters.

♪♪ ♪♪ Resident tigers will continue to gather because there is plenty to go around, for days.

♪♪ It's a leisurely feast, rare in the ocean realm.

♪♪ ♪♪ ♪♪ The 50-foot leviathan is slowly devoured as the tigers search for the softest places to feed on first.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ Then, an out-of-towner arrives.

♪♪ She's not a frequent flier to Hawaii, but she's not a stranger, either.

♪♪ She's a well-known great white female that goes by the name Deep Blue.

♪♪ She's one of the largest white sharks ever seen, weighing at least 2.5 tons, over 8 feet tall and 20 feet long.

♪♪ She often hangs around Guadalupe Island, in Mexico, but this is the first time she's been seen here.

♪♪ And, now, she is so intimidating, she gets the whale carcass to herself.

♪♪ ♪♪ ♪♪ No one knows why she's traveled all the way to Hawaii, but she appears to be pregnant.

Perhaps she, too, is searching for the perfect place to give birth.

♪♪ In this place of battle and beauty, among the violent volcanoes and vibrant coral reefs, so many sharks have made Hawaii their home.

♪♪ Perhaps the most formidable of all, the great white, will find paradise here, too.

♪♪ To order this "Nature" program on DVD, visit shopPBS or call 1-800-PLAY-PBS.

This program is also available on Amazon Prime Video.

♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.

♪♪