NARRATOR: PACIFIC MEANS PEACEFUL.

IT'S ANYTHING BUT.

THE PACIFIC OCEAN IS A DANGEROUS WORLD... WHERE DEATH REACHES FOR THE SKY... AND LIFE PUSHES ITS LIMITS... WHERE YOU CAN'T TRUST YOUR EYES... AND WHERE TITANS CLASH.

[WHALE SONG] 64 MILLION SQUARE MILES.

1/3 OF OUR PLANET.

THE BIGGEST OCEAN ON EARTH IS A PLACE OF VIOLENCE.

NARRATOR: BIKINI ATOLL SITS LIKE AN IDYLLIC CIRCLE OF SAND IN THE BLUE WATERS OF THE PACIFIC, BUT BELOW BIKINI, THE REMAINS OF VIOLENCE.

THE "U.S.S.

SARATOGA" WAS THE PRIDE OF THE U.S. NAVY IN WORLD WAR II.

IN HER PRIME, SHE SUFFERED TWO TORPEDO HITS, 4 BOMB BLASTS, AND 6 KAMIKAZE ATTACKS.

NOW SHE RESTS ON THE BOTTOM OF BIKINI'S LAGOON... ONE GRAVE AMONG MANY.

BUT IT WASN'T THE WAR THAT SUNK THEM.

THEY WERE GUINEA PIGS IN THE MOST VIOLENT EXPERIMENTS EVER CONDUCTED.

[RADIO CHATTER] BIKINI ATOLL IS A SPECK IN THE MIDDLE OF NOWHERE...

WHICH MADE IT AN IDEAL CANDIDATE FOR NUCLEAR TESTING.

AFTER WORLD WAR II, 23 NUCLEAR WEAPONS WERE DETONATED HERE.

[CLOCK TICKING] MAN: 4, 3, 2, 1.

[BOOM] [BOOM] NARRATOR: THE GREATEST WAS 1954's CASTLE BRAVO TEST, A TRIAL RUN FOR THE FIRST DRY-FUEL THERMONUCLEAR BOMB... ONE OF THE LARGEST MILITARY EXPLOSIONS IN HISTORY AND A THOUSAND TIMES MORE POWERFUL THAN THE HIROSHIMA BOMB.

A FIREBALL 3 MILES WIDE ANNIHILATED EVERY LIVING THING IN THE AIR, ON LAND, AND IN THE SEA FOR MILES AROUND.

MAN: THIS IS BRAVO CRATER, GROUND ZERO FOR THE MOST VIOLENT THING WE HAVE EVER DONE TO THE OCEAN.

NARRATOR: 6 DECADES LATER, STANFORD UNIVERSITY BIOLOGIST DR. STEVE PALUMBI INVESTIGATES HOW BIKINI HAS RECOVERED FROM OUR NUCLEAR ASSAULTS.

PALUMBI: A 15-MEGATON HYDROGEN BOMB BLEW THIS MILE-WIDE CRATER INTO THE REEF, A SCAR ON THE OCEAN AND THE PLANET THAT YOU CAN SEE FROM SPACE.

NARRATOR: EVEN AFTER 60 YEARS OF EROSION FROM TIDES AND STORMS, THE CRATER WALLS REMAIN.

IT'S BARREN... THEN SIGNS OF LIFE.

PALUMBI: THERE'S CORALS GROWING, THERE'S BIG CORALS GROWING.

LOTS OF FISH SWIRLING AROUND.

THE MOST IMPORTANT QUESTION REALLY IS, IS IT ALL BETTER?

NARRATOR: IT'S A TIMELESS QUESTION IN THE PACIFIC, PERHAPS THE MOST VIOLENT PLACE ON EARTH.

WORLD SUPERPOWERS ARE NOT THE ONLY GIANTS THAT HAVE CLASHED IN THE PACIFIC.

NATURE CREATES HER OWN BATTLES.

[WHALES SINGING] EVERY WINTER, HUMPBACK WHALES COMPLETE A 2,500-MILE MIGRATION FROM THEIR FEEDING GROUNDS IN THE NORTH.

IN A VITAL BREAK FROM THEIR USUALLY SOLITARY LIVES, THEY GATHER TO MATE.

ADULT MALES OUTNUMBER RECEPTIVE FEMALES, SO THERE'S COMPETITION AMONG THE BULLS.

THEY ALL WANT THE PRIVILEGE OF BEING HER ESCORT AND SWIMMING ALONGSIDE HER BECAUSE WHEN SHE'S READY TO MATE, THE MALE ALONGSIDE PROBABLY HAS THE BEST CHANCES... [SINGING CONTINUES] BUT TO HOLD THAT SPOT, HE'LL HAVE TO FEND OFF ASSAULTS FROM THE LARGEST INTERLOPERS ON EARTH... BEGINNING A VIOLENT EVENT KNOWN AS THE HEAT RUN.

THE TESTOSTERONE-FUELED SINGLE MALES JOCKEY FOR THE COVETED ROLE OF ESCORT, TRYING TO FORCE THEMSELVES BETWEEN HER AND HER SUITOR.

HE RELEASES A BUBBLE STREAM, A WARNING TO RIVALS-- "DON'T CROSS THE LINE."

AS THE COMPETITION BUILDS, THE MALES BECOME 40-TON WRECKING BALLS IN THE PACIFIC'S MOST GARGANTUAN BRAWL.

HE OVERPOWERS HIS RIVAL, FORCING HIM DOWN, DEMANDING RETREAT.

[WHALES SINGING] HE CAN RETURN TO HIS PARTNER'S SIDE...

BUT THIS FIGHT FOR HER IS ONE OF MANY.

THE OTHER MALES ARE RESTING.

THE RUN HAS ONLY JUST BEGUN.

[BIRDS AND INSECTS CHIRPING] THROUGHOUT THE PACIFIC, MALES CLASH OVER BREEDING RIGHTS.

ON THIS REMOTE TROPICAL ISLAND, PREHISTORIC REPTILES LURK IN THE SHALLOWS, CONCEALING BODIES 20 FEET LONG AND WEIGHING UP TO ONE TON.

SALTWATER CROCODILES ARE TERRITORIAL... AND THE LARGEST MALES RULE THEIR DOMAIN WITH AN IRON JAW.

FOR A SUBORDINATE MALE, THE ONLY WAY TO TAKE THE THRONE IS TO TAKE ON THE KING.

[GROWLING] [FLIES BUZZING] THIS LARGE MALE WAS LUCKY TO ESCAPE WITH ONLY INJURIES.

PITY THE JUVENILES.

DOMINANT MALES ARE KNOWN TO HAVE THEM FOR LUNCH.

LESS THAN 1% OF SALTIES MAY REACH ADULTHOOD.

IF THIS YOUNG MALE HAS A FUTURE, IT WON'T BE HERE.

SO BEGINS A MIGRATION RARELY WITNESSED AND ONLY RECENTLY UNDERSTOOD.

HIS VOYAGE MIGHT COVER MORE THAN 10 MILES A DAY AND LAST FOR WEEKS.

SALTIES EXPERTLY NAVIGATE THE OCEAN'S TIDES AND CURRENTS, BUT HE'S NOT BUILT FOR CONTINUOUS SWIMMING.

WHEN THE CURRENT WORKS AGAINST HIM, HE GIVES IN AND RESTS.

MANY REPTILES CAN DOZE IN A STATE CALLED UNIHEMISPHERIC SLEEP...

WHEN THE LEFT AND RIGHT SIDES OF THEIR BRAIN TAKE TURNS SLEEPING.

HE HOLDS HIS BREATH FOR UP TO AN HOUR, BUT THE CONSTANT IMMERSION DOES BRING PROBLEMS.

HE MIGHT BE NAMED AFTER SALTWATER, BUT HE'S NOT IMPERVIOUS TO SALT.

SPECIAL GLANDS ON HIS TONGUE EXCRETE THE EXCESS SALT THAT BUILDS UP IN HIS BODY... AND WITH A SLOW METABOLISM, HE CAN SURVIVE WEEKS WITHOUT FOOD, MAKING THE JOURNEY POSSIBLE.

HE NEEDS A REFUGE FROM VIOLENCE, AND THIS NEW HOME MAY ONE DAY BECOME HIS OWN DOMAIN...

BUT NOT ALL ISLANDS IN THE PACIFIC ARE SO HOSPITABLE.

IN CHINA'S BOHAI SEA FLOATS A FRAGMENT OF LAND CALLED SHEDAO.

ONCE ATTACHED TO THE PENINSULA NEARBY, IT NOW STANDS ALONE.

SHEDAO MEANS SNAKE ISLAND.

DEADLY PIT VIPERS... 20,000 OF THEM.

MOST OF THE YEAR, THERE'S NO FOOD FOR THEM.

ALL SUMMER, THEY STARVE AND SLEEP... UNTIL AUTUMN.

[BIRDS CALLING] FOR MILLIONS OF SONGBIRDS MIGRATING SOUTH FROM SIBERIA, THE ISLAND IS A REST STOP... [CHIRPING] BUT THE NEEDS OF THE TIRED AND THE HUNGRY ARE ABOUT TO INTERSECT.

[BIRD CHIRPING] AT DAWN, THE VIPERS SEEK OUT THE BEST PERCHES.

EVEN A LOWLY TWIG WILL DO.

20,000 BOOBY TRAPS WAITING FOR SONGBIRDS.

IT TAKES SEVERAL DAYS TO DIGEST THE MEAL...

BUT TO MAXIMIZE THE OPPORTUNITY...

THEY CAN SWALLOW UP TO 3 BIRDS... ONE AFTER ANOTHER.

THE WINDOW FOR FOOD IS SO BRIEF, THE SNAKES HUNT NONSTOP.

FOR THE NEXT TWO WEEKS, THEY FOLLOW THE DEADLY ROUTINE... [BIRDS CHIRPING] CLIMB UP AT DAWN AND WAIT FOR A MEAL TO BE DELIVERED.

[CHIRPING STOPS] [CHIRPING RESUMES] BY THE TIME THE MIGRATION RESUMES, THE ISLANDERS ARE STUFFED TO BURSTING.

ALL THROUGH THE WINTER MONTHS, THEY'LL REST... UNTIL SPRING, WHEN THE MIGRATORS RETURN ON THEIR JOURNEY BACK NORTH.

AT OTHER HOTSPOTS IN THE BIG PACIFIC, DEATH IS A DAILY FACT OF LIFE.

IN INDONESIA'S LEMBEH STRAIT, A STRONG, CONSTANT CURRENT KEEPS REEFS FROM FORMING...

BUT LIFE STILL THRIVES.

IT NOT ONLY THRIVES, IT TEEMS.

THOUSANDS OF SPECIES COMPETE FOR SPACE AND FOOD IN A WATERWAY ABOUT 1/3 OF A MILE WIDE.

BECAUSE OF THE CURRENT, MOST CREATURES HERE MUST LIVE ON THE SEABED OR CLOSE TO IT.

IT'S LIKE CRAMMING ALL THE RESIDENTS OF A HIGH-RISE ON THE GROUND FLOOR...

BUT ALMOST EVERY NEIGHBOR WANTS TO EAT YOU.

IT'S CREATED AN EVOLUTIONARY ARMS RACE, A PREDATORY COMPETITION RUNNING OUT OF CONTROL.

ANIMALS HERE HAVE EVOLVED THEIR OWN GIMMICKS FOR HUNTING OR HIDING.

ONE HUNTER HIDES IN PLAIN SIGHT.

THE FROGFISH'S STUBBY FINS HAVE EVOLVED INTO FEET, BUT THAT'S JUST A TOE IN THE WATER COMPARED TO ITS REAL TALENT.

WHEN IT REACHES ITS DESTINATION, IT BLENDS IN NEXT TO ITS DOPPELGANGER SPONGE AND WAITS.

MORE THAN A DOZEN SPECIES OF FROGFISH LIVE IN THE LEMBEH STRAIT...

INCLUDING THE HAIRY FROGFISH.

THE FISH IT PREYS ON SEEK PROTECTION AMONG THE VENOMOUS SPINES OF FIRE URCHINS...

SO THE HAIRY FROGFISH TURNS DARK AND SPINY, BECOMING JUST ANOTHER URCHIN HIMSELF.

NOW HE CASTS HIS BAIT, A WORM-LIKE LURE... A DEADLY OFFERING.

IN A NEIGHBORHOOD THIS ROUGH, EVEN A FORTIFIED BODY CAN'T GUARANTEE PROTECTION.

CRABS HERE ARE ON EVERY MENU.

TO STAY ALIVE, THE CARRIER CRAB RESORTS TO KIDNAPPING.

SPECIAL ARMS SCOOP THE URCHIN UP FROM BELOW, AVOIDING THE DANGEROUS SPINES.

HE HAULS HIS GRUDGING HOSTAGE EVERYWHERE, AND PREDATORS LEAVE HIM ALONE.

IN THE CROWDED CONDOMINIUMS OF LEMBEH, SOME KILLERS LURK IN THE BASEMENT.

THIS HIDEOUS MASK BELONGS TO THE VENOMOUS STARGAZER.

HE'S WAITING TO EMPLOY A DEADLY TRICK.

ANOTHER BASEMENT DWELLER, THE BOBBIT WORM, A RELATIVE OF THE SIMPLE EARTHWORM.

BURIED IN THE SAND, A BODY UP TO 10 FEET LONG.

ALL THAT PROTRUDES IS A SET OF JAWS SURROUNDED BY SENSORY TENTACLES.

IF COMPETITION BREEDS EXCELLENCE, LEMBEH STRAIT IS LETHALLY EXCELLENT INDEED.

[RUMBLING] THE PACIFIC IS ENCIRCLED BY THE RING OF FIRE, A 25,000-MILE ARC OF VIOLENCE...

CONTAINING 3/4 OF THE WORLD'S ACTIVE VOLCANOES... MORE THAN 450 OUTLETS FOR NATURE'S MOLTEN TEMPER.

ALL THIS SEISMIC FURY IS CAUSED BY THE CEASELESS GRINDING OF THE EARTH'S LARGEST TECTONIC PLATE, THE PACIFIC PLATE.

THE RING OF FIRE CAN DESTROY LIFE, BUT IT ALSO CREATES IT.

30 MILES OFF NEW ZEALAND, WHITE ISLAND RUMBLES FROM CONSTANT INDIGESTION...

THE TIP OF A VOLCANO THAT'S BEEN ACTIVE FOR 150,000 YEARS.

CRACKS IN THE CRATER WALLS, KNOWN AS FUMAROLES, BLOW HOT GAS LIKE A JET ENGINE... LEAVING BEHIND TOXIC SULFUR DEPOSITS.

IT'S HARD TO BELIEVE HUMANS ONCE LIVED HERE.

IN 1913, A QUARRY OPENED ON WHITE ISLAND TO EXTRACT SULFUR FOR FERTILIZER.

THE FACTORY WAS BUILT ON THE CRATER'S FLOOR.

ONE MINER DESCRIBED THE ISLAND AS "THE WORST HELL ON EARTH, "A PLACE WHERE ROCKS EXPLODED, "WHERE TEETH WENT BLACK IF THEY WEREN'T CLEANED "3 TIMES A DAY, AND WHERE THE LAND SHOOK VIOLENTLY."

[RUMBLING] A YEAR AFTER THE ENTERPRISE BEGAN, DISASTER STRUCK.

PART OF THE CRATER WALL COLLAPSED, AND A SUPER-HEATED AVALANCHE KILLED EVERYONE.

TRACES OF THE LOFTY ATTEMPT AT MINING STILL REMAIN...

BUT NO HUMANS HAVE LIVED HERE SINCE...

BUT THE ISLAND DOES HAVE ITS INHABITANTS...

SOME OF THE HARDIEST ANIMALS ON EARTH IN THE CRATER LAKE, BUBBLING AWAY AT 122 DEGREES FAHRENHEIT.

IT'S AT LEAST 10 TIMES MORE ACIDIC THAN PURE VINEGAR, YET ITS GREEN TINGE COMES FROM EXTREMOPHILES, PRIMITIVE MICROBES THAT CAN SURVIVE IN CONDITIONS HOSTILE TO NORMAL LIFE.

THE MICROBES HERE CAN NEUTRALIZE THE ACID AND CARRY OUT THEIR LIFE CYCLES IN TEMPERATURES THAT WOULD KILL MOST LIVING THINGS, BUT FOR THESE MICROBES, CONDITIONS LIKE THESE ARE NOT NEW.

NEARLY 4 BILLION YEARS AGO WHEN EARTH WAS AS INHOSPITABLE AS WHITE ISLAND, THE FIRST LIFE TO EVOLVE LOOKED VERY MUCH LIKE THESE EXTREMOPHILES.

SURVIVAL IN HELL MAY BE A HOMECOMING FOR MICROBES...

BUT BIGGER ANIMALS HAVE DEVELOPED THE SAME ABILITY.

TURTLE MOUNTAIN ISLAND SITS WHERE TWO TECTONIC PLATES COLLIDE.

BENEATH ITS MILKY SURFACE IS A LABYRINTH OF HYDROTHERMAL VENTS.

THE EXHAUST OF A GIGANTIC UNDERWATER VOLCANO THAT PUMPS OUT WATER ABOVE BOILING AT 240 DEGREES FAHRENHEIT AND A CONSTANT SPEW OF SULFUROUS GASES, THIS IS ONE OF THE MOST TOXIC ENVIRONMENTS ON THE PLANET... AND YET LIFE PERSISTS.

THESE ARE SULFUR VENT CRABS.

THEY LIVE ALONG THE EDGE OF THE VENTS, WHERE THE WATER DOESN'T BOIL BUT IS STILL TOO TOXIC FOR ANY OTHER LIFE.

THEY'VE EVOLVED A UNIQUE ABILITY TO BREAK DOWN AND NEUTRALIZE SULFURIC ACID.

NOT ONLY DO THEY SURVIVE IN THIS DEAD ZONE, THEY USE IT TO THEIR ADVANTAGE.

THE POISONOUS GASES INSTANTLY KILL PASSING ZOOPLANKTON.

IT FALLS LIKE A MARINE SNOW.

THE FLATTENED TIPS OF THEIR PINCERS ARE UNIQUELY ADAPTED TO GATHER THE MORSELS.

THE VENT CRABS ARE ONE OF THE PACIFIC'S MASTERS OF SURVIVAL, BUT NOT ALL OF HER DANGERS HAVE BEEN SO READILY CONQUERED.

THE PACIFIC OCEAN IS GROUND ZERO FOR THE BIGGEST STORMS ON EARTH.

IN THE NORTH, WE CALL THEM TYPHOONS, IN THE SOUTH, CYCLONES-- ENORMOUS TROPICAL STORMS UNLEASHED MORE THAN TWO DOZEN TIMES A YEAR.

CYCLONE DEBBIE GREW OUT OF THE CORAL SEA OFF PAPUA NEW GUINEA IN MARCH OF 2017.

OVER 6 DAYS, IT GREW TO A STORM OF ENORMOUS PROPORTIONS, WANDERING ACROSS THE PACIFIC BEFORE IT TURNED STRAIGHT FOR AUSTRALIA'S QUEENSLAND COAST.

AT LANDFALL, IT DELIVERED WIND GUSTS OF 160 MILES AN HOUR, A STORM SURGE OF ALMOST 9 FEET.

63,000 HOMES WITHOUT POWER, ALMOST 40 INCHES OF RAIN IN TWO DAYS.

12 PEOPLE DEAD... AND DEBBIE DOESN'T EVEN MAKE THE RECORD BOOKS.

THE PACIFIC CHURNS OUT STRONGER STORMS THAN THIS EVERY YEAR.

[ALARM BLARING] DON'T...

THERE ARE SUPER-TYPHOONS THAT CAN RELEASE 200 TIMES MORE ENERGY THAN ALL THE POWER STATIONS ON EARTH... [SIRENS] BUT THE PACIFIC, ITS PEOPLE, AND ITS ANIMALS PERSIST.

THEY REPAIR AND RECOVER.

[INDISTINCT CHATTER] [FLIES BUZZING] FOR ONE ANIMAL WHEN CYCLONES RECEDE, THEY LEAVE GIFTS BEHIND.

BLUEBERRY HERMIT CRABS LIVE ON ISLANDS ACROSS THE WESTERN PACIFIC.

AS THEY GROW, THE CRABS HUNT FOR ROOMIER HOUSING, A SEARCH IT REPEATS THROUGHOUT ITS LIFE.

IN THEIR CONSTANT QUEST FOR HOME IMPROVEMENT, THE CRABS HAVE LEARNED TO EXPLOIT THE RUBBLE AND DEBRIS OF DISASTER.

MANMADE MATERIALS THAT POLLUTE THE PACIFIC CAN ALSO PROVIDE PROTECTION THAT'S HARD TO BEAT.

FOR THE COLOR-SAVVY AND TACTILE CRABS, FINDING THE PERFECT FIT TAKES TIME.

THE HUES, SHAPES, AND MATERIALS ARE ENDLESS.

UPGRADED HOUSING FOR THE BLUEBERRY HERMIT, OPPORTUNITY IN THE WAKE OF VIOLENCE.

[HORN HONKS] IN CHINA, EVEN HUMANS ARE LEARNING TO MAKE THE MOST OF THE VIOLENT PACIFIC.

SEPTEMBER, AND HANGZHOU BAY WAITS FOR THE ANNUAL RETURN OF AN ANCIENT SEA MONSTER.

TEMPLES WERE BUILT TO WORSHIP IT, AND PAGODAS WERE BUILT TO PLACATE IT.

FOR CENTURIES, IT'S BEEN KNOWN AS THE SILVER DRAGON... A PREDICTABLE YET POTENTIALLY DESTRUCTIVE WALL OF WATER THAT GROWS INTO THE WORLD'S LARGEST TIDAL WAVE.

UNLIKE TSUNAMIS, WHICH ARE TRIGGERED BY EARTHQUAKES, THIS RARE PHENOMENON IS BROUGHT ON BY THE LUNAR CYCLE AND FORMS WHERE THE BAY NARROWS AND FUNNELS THE INCOMING TIDE...

CONTINUOUSLY AMPLIFYING ITS SIZE AND SPEED.

BUILDING TO 30 FEET HIGH AND RACING AT 25 MILES AN HOUR, IT FORCES ITS WAY UP THE MOUTH OF THE QIANTANG RIVER.

[HORN HONKS] SQUARE IN ITS PATH LIES HANGZHOU, POPULATION MORE THAN 6 MILLION... ONE OF CHINA'S BIGGEST CITIES.

IT'S AN IMMOVABLE OBJECT RIGHT IN THE WAY OF AN IRRESISTIBLE FORCE.

THE CHINESE BUILT SEAWALLS TO TAME THE SILVER DRAGON BACK IN THE TENTH CENTURY.

A QING DYNASTY WALL FROM 1720 PROTECTS THE CITY TODAY, YET 5 PEOPLE A YEAR STILL DIE...

BUT A FEW BRAVE SOULS NOW DARE TO RIDE THE DRAGON.

THE QIANTANG RIVER IS HOME TO ONE OF THE WORLD'S MOST DARING COMPETITIONS.

IN A SPORT WHERE RIDES ARE USUALLY MEASURED IN SECONDS, THE DRAGON'S BACK CAN CHALLENGE A SURFER FOR A DEATH-DEFYING 20 MINUTES.

ONLY THE EXPERT AND THE LUCKY WILL SURVIVE.

BUT OF ALL THE VIOLENCE AND DANGER IN THE PACIFIC, IT'S STILL THE HUMAN-CREATED VIOLENCE THAT STACKS UP AS THE MOST CONFRONTING.

MILNE BAY ON THE EASTERN EDGE OF PAPUA NEW GUINEA.

VILLAGERS SHOW THE WAY TO A HAUNTING RELIQUARY.

DEEP IN THE JUNGLE, AN UNINVITING CLEFT IN THE ROCKS REVEALS A CRYPT, THE RESTING PLACE OF HUNDREDS OF HUMAN SKULLS...

SOME CAREFULLY ARRANGED, OTHERS CARELESSLY TOSSED ON THE PILE... A PLACE SO ANCIENT THAT THE CAVE IS SLOWLY CONSUMING THE SKULLS, WRAPPING THEM IN CRYSTAL.

THIS CAVE IS NOT A SECRET, BUT HOW THESE SKULLS CAME TO BE HERE IS.

SOME WHISPER, "THE TROPHY ROOMS OF HEAD HUNTERS."

EXPLORERS IN THE 1950s DESCRIBED WARRIORS ALONG PAPUA'S COAST SETTING OUT TO AMBUSH OTHER TRIBES AND BRING BACK THEIR REMAINS AS TALISMANS.

SOME ACCOUNTS DESCRIBED CANNIBALISM.

[THUD, SPLAT] THERE ARE SKULLS WITH WOUNDS THAT SUGGEST VIOLENCE, BUT OTHERS SAY THE CAVE IS WHERE THE LOCAL PEOPLE ONCE HONORED THEIR ANCESTORS... PERHAPS A PLACE FOR A REUNION BETWEEN THE LIVING AND THE DEAD.

YAAH!

A CAVE OF VIOLENCE OR A CAVE OF MEMORIES, WE MAY NEVER KNOW.

[SHOUTS IN NATIVE LANGUAGE] NARRATOR: THE PACIFIC IS SKILLED AT COVERING UP THE PAST, AND WITH EACH PASSING YEAR, THE TRUTH IS BURIED WITH IT.

THESE ARE ONE OF THE FEW SIGNS THAT PEOPLE EVER LIVED ON BIKINI ATOLL... BUNKERS BUILT TO OBSERVE THE NUCLEAR BLASTS DURING THE FORTIES AND FIFTIES.

THE RADIATION SPREAD AROUND THE GLOBE.

PALUMBI: 1/7 OF THE WORLD'S EXTRA RADIATION CAME FROM HERE.

IT SPREAD ALL OVER THE PLANET, BUT IT'S STILL CONCENTRATED RIGHT HERE.

NARRATOR: AFTER 23 NUCLEAR TESTS DURING THE COLD WAR, THE SOIL ON BIKINI ATOLL IS A RADIOACTIVE HOT ZONE.

THE AIR IS SAFE TO BREATHE, THE WATER'S SAFE TO SWIM IN, BUT LIVING HERE IS IMPOSSIBLE.

STANFORD UNIVERSITY'S DR. STEVE PALUMBI IS STUDYING THE ISLAND'S RECOVERY.

PALUMBI: PEOPLE KEPT TRYING TO MOVE BACK HERE, BUT THEY COULDN'T.

IT'S THE RADIATION THAT THE BOMBS LEFT.

IT SEEPS INTO EVERYTHING.

NARRATOR: ALL OF BIKINI'S PLANTS ARE LADEN WITH CESIUM-137, A RADIOACTIVE ISOTOPE THAT CAUSES CANCER.

EATING ANYTHING FROM THE ISLAND COULD BE DEADLY.

THE COCONUTS HAVE ONE OF THE HIGHEST LEVELS OF RADIOACTIVITY...

BUT ONE RESIDENT GORGES ON THE TAINTED FOOD...

THE COCONUT CRAB.

PALUMBI: THEY DIDN'T GET THE MEMO THAT THERE WAS CESIUM-137 IN THE COCONUTS, AND SO THEY'RE RADIOACTIVE, TOO.

THE DNA OF THIS ANIMAL PROBABLY HAS A RECORD OF THE CESIUM-137 DECAYING AND RIPPING THROUGH THE GENETICS.

NARRATOR: BIKINI'S CRABS WERE WIPED OUT DURING THE NUCLEAR TESTS, BUT COCONUT CRABS LAY THEIR EGGS IN THE OCEAN, AND THE LARVAE DEVELOP IN THE SEA.

SOME FLOATED ASHORE TO REPOPULATE THE ISLAND, ACCUMULATING THE INVISIBLE SCARS OF RADIATION.

CORAL SAMPLES.

AS A MARINE BIOLOGIST, PALUMBI HAS COME TO COLLECT CORAL SAMPLES, LONG-LIVED ANIMALS THAT MAY BEAR MUTATIONS.

[RESPIRATOR HISSES] PALUMBI: THESE HUGE CORALS DOWN HERE HAVE PROBABLY BEEN GROWING SINCE JUST AFTER THE EXPLOSION, AND SO THEY'RE A RECORDER OF WHAT THE ENVIRONMENT'S BEEN LIKE EVER SINCE.

NARRATOR: THE CORALS ABSORBED RADIATION INTO THEIR TISSUES AND SKELETON.

DNA ANALYSIS OF SAMPLES WILL REVEAL ANY GENETIC MUTATIONS.

PALUMBI: WE'RE GONNA LOOK AT THESE ANIMALS WHO HAVE BEEN LIVING HERE THE WHOLE TIME.

WE'RE GONNA LOOK AT THEIR MUTATIONS, AND WE'RE GONNA LOOK TO SEE WHAT IT WAS LIKE FOR THEM TO BE LIVING HERE EVER SINCE THOSE BOMBS WENT OFF.

NARRATOR: FOR COMPARISON, PALUMBI AND HIS TEAM HAVE COLLECTED A CONTROL GROUP OF UNRADIATED CORALS FROM AMERICAN SAMOA, 2,400 MILES AWAY.

WOMAN: BY LOOKING AT THE CORALS THAT HAVE NOT EXPERIENCED ANY SORT OF RADIATION, WE CAN THEN COMPARE THE CORALS AT BIKINI THAT HAVE EXPERIENCED RADIATION AND SAY, "WELL, IS THIS HIGHER THAN THE BASELINE RATE "IN AMERICAN SAMOA, OR IS IT ACTUALLY KIND OF THE SAME?"

NARRATOR: RESEARCHER ELORA LOPEZ IS LOOKING FOR GENETIC CHANGES, THE TELL-TALE SIGN OF RADIOACTIVE DAMAGE.

LOPEZ: MY BIGGEST INTEREST IS REALLY IN HOW WILD POPULATIONS, SUCH AS CORALS OR ALL SORTS OF OTHER THINGS, ARE AFFECTED BY HUMAN ACTIONS.

NARRATOR: MUCH OF BIKINI ATOLL'S MARINE LIFE HAS RETURNED, AND MANY OF ITS REEFS ARE THRIVING.

INVERTEBRATES, DOZENS OF SPECIES OF FISH...

EVEN APEX PREDATORS.

PALUMBI: SHARKS ARE THE TOP PREDATORS ON REEFS, AND USUALLY, THERE'S A LOT OF THEM.

NARRATOR: A SIGN OF A HEALTHY ECOSYSTEM...

BUT SOMETHING ABOUT THESE NURSE SHARKS IS ODD.

A NORMAL ONE HAS TWO DORSAL FINS, THE LARGER ONE IN FRONT.

PALUMBI: THERE ARE INDIVIDUAL NURSE SHARKS IN THE MARSHALL ISLANDS THAT ONLY HAVE ONE DORSAL FIN.

POPULAR BELIEF IS THAT RADIATION CAUSES MUTATIONS, AND YOU KNOW WHAT?

IT'S TRUE.

SO IF YOU THINK ABOUT IT, DO WE HAVE MUTANT SHARKS ON BIKINI ATOLL MISSING A FIN?

IS THAT WHAT WE'VE GOT?

AND THE ANSWER IS POSSIBLY.

I'VE NEVER SEEN ANYTHING LIKE IT BEFORE, AND THAT MEANS WE HAVE A SCIENTIFIC MYSTERY TO UNRAVEL.

NARRATOR: HOW MUCH VIOLENCE CAN WE THROW AT THE PACIFIC BEFORE IT STOPS BOUNCING BACK?

THAT'S A MYSTERY, TOO.

BUT AROUND THE RING OF FIRE, HOPE SHOWS ITS FACE.

A MITSUBISHI ZERO, A JAPANESE WAR MACHINE... ONCE ONE OF THE DEADLIEST HUNTERS IN THE PACIFIC.

PACKS OF ZEROES RACKED UP KILLS BY THE THOUSANDS.

THEY LITTER THE BOTTOM OF THE PACIFIC FROM THE CORAL SEA TO TOKYO.

TODAY INSTEAD OF TAKING LIFE, THEY GIVE IT.

AN ARTIFICIAL REEF, HOME TO AN ECLECTIC COMMUNITY.

THE SKUNK CLOWNFISH...

THE CORAL TROUT...

THE ANEMONE SHRIMP.

IN TIME, THE WRECKAGE WILL VANISH, LEAVING BEHIND A PLANE-SHAPED MASS OF CORAL AND SPONGES.

THE PACIFIC REPAIRS HERSELF, AND ON THE REMAINS OF VIOLENCE, LIFE REACHES OUT.

NARRATOR: NEXT TIME ON "BIG PACIFIC"...

THE BIGGEST MOUTH IN THE OCEAN... A HUNTER THAT MUST EAT NONSTOP... AND A GIANT THAT MAY NOT EAT FOR A YEAR.

IT'S EAT OR BE EATEN IN THE BIG PACIFIC.

"BIG PACIFIC" IS AVAILABLE ON BLU-RAY AND DVD.

THE COMPANION BOOK IS ALSO AVAILABLE.

TO ORDER, VISIT SHOPPBS.ORG OR CALL 1-800-PLAY-PBS.

THIS PROGRAM IS ALSO AVAILABLE FOR DOWNLOAD ON ITUNES.