0:00:06 > 0:00:09There's an ocean where giants gather to feast...
0:00:13 > 0:00:16..where people battle the planet's roughest seas.
0:00:19 > 0:00:24It stretches nearly 10,000 miles from Arctic to Antarctic.
0:00:30 > 0:00:31From tropical shallows...
0:00:33 > 0:00:34..to mysterious depths.
0:00:41 > 0:00:42It's an ocean of extremes.
0:00:46 > 0:00:49Engine room for storms 1,000 miles across.
0:00:51 > 0:00:54It's also a sanctuary for the vulnerable.
0:00:57 > 0:01:00People and animals brave this unpredictable ocean...
0:01:02 > 0:01:05..risking it all for rich rewards.
0:01:07 > 0:01:12This is the Atlantic - the wildest ocean on Earth.
0:01:30 > 0:01:35The Caribbean, the Atlantic's sun-drenched paradise.
0:01:45 > 0:01:49Its warm, shallow waters offer shelter and plenty of food.
0:01:59 > 0:02:04The perfect place for this two-year-old Atlantic spotted dolphin to grow up.
0:02:08 > 0:02:11The seas around him are bursting with life.
0:02:19 > 0:02:23It's the richest corner of the Atlantic.
0:02:23 > 0:02:26But paradise comes at a cost.
0:02:36 > 0:02:42Over the next nine months, the sun's energy will push life here to its limits.
0:02:44 > 0:02:49Caribbean heaven will soon turn to hell.
0:03:07 > 0:03:11The sun is the tropical Atlantic's engine.
0:03:19 > 0:03:22It heats the ocean and the coast of Africa
0:03:22 > 0:03:26right across to the Caribbean, 3,000 miles away.
0:03:34 > 0:03:38Here, there are huge expanses of crystal-clear sea.
0:03:51 > 0:03:55There are coral reefs,
0:03:55 > 0:03:59meadows of seagrass and mangrove forests.
0:04:02 > 0:04:06There's a wider variety of marine life here than anywhere else in the Atlantic.
0:04:10 > 0:04:13Living here can bring rich rewards.
0:04:21 > 0:04:25Right now, it's February - the Caribbean's coolest month.
0:04:26 > 0:04:32Even so, these shallows off the Bahamas are a balmy 23 degrees
0:04:32 > 0:04:33and the water's full of sound.
0:04:36 > 0:04:42CLICKING AND WHISTLING
0:04:44 > 0:04:46The chatter of Atlantic spotted dolphins.
0:04:49 > 0:04:52CLICKING AND WHISTLING
0:04:59 > 0:05:01It's a safe refuge for them -
0:05:01 > 0:05:04the deeper waters are patrolled by sharks.
0:05:13 > 0:05:17Dolphins are highly social and play together and hunt together
0:05:17 > 0:05:20in tight-knit groups, sometimes 50-strong.
0:05:26 > 0:05:28These two mothers have teamed up
0:05:28 > 0:05:32so their calves can play and learn from each other.
0:05:32 > 0:05:34The calves are still suckling from their mums
0:05:34 > 0:05:36and yet to fully develop their spots.
0:05:42 > 0:05:46They've plenty of time to learn the ins and outs of dolphin social life.
0:05:49 > 0:05:54They must learn a huge number of complex clicks and whistles.
0:05:54 > 0:05:57CLICKING AND WHISTLING
0:05:59 > 0:06:01Body language is important, too.
0:06:04 > 0:06:07Play-biting helps build social bonds,
0:06:07 > 0:06:10one of the first ways that young dolphins learn to interact.
0:06:23 > 0:06:28Then there's fin-rubbing. Scientists compare it to a handshake or a hug.
0:06:34 > 0:06:39It's all great fun but they're learning vital lessons.
0:06:54 > 0:07:00From February on, the Caribbean gets a little warmer every day.
0:07:00 > 0:07:05Good news for another marine mammal that simply can't survive without the heat.
0:07:13 > 0:07:14A manatee.
0:07:18 > 0:07:24Distant relative of the elephant, she's 3m long and weighs in at almost a tonne.
0:07:27 > 0:07:31But despite her bulk, she has very little blubber to keep her warm.
0:07:31 > 0:07:35She lives here because the water never drops below 20 degrees.
0:07:35 > 0:07:37If it did, she'd die.
0:07:40 > 0:07:45Lots of manatees overwinter in warm river estuaries.
0:07:45 > 0:07:50Now, as sea temperatures rise, they spread along the Caribbean coast
0:07:50 > 0:07:54in search of their favourite food - seagrass.
0:07:56 > 0:08:03It covers huge areas of these shallows and the warmer and sunnier it gets, the faster it grows.
0:08:07 > 0:08:13Over the coming months, she'll spend seven hours a day grazing these marine meadows.
0:08:13 > 0:08:15It's manatee heaven - for now.
0:08:22 > 0:08:24Change is on the way.
0:08:28 > 0:08:31By April, the sun is just a little bit more intense.
0:08:31 > 0:08:35A small change with big effects.
0:08:38 > 0:08:41In the deep water beyond Belize's barrier reef,
0:08:41 > 0:08:45the growing heat triggers a spectacular annual event.
0:08:56 > 0:08:58Snappers.
0:08:58 > 0:09:04They've gathered here in this one place for one hour for one reason.
0:09:06 > 0:09:12Snappers are usually solitary and live over 20m beneath the surface.
0:09:12 > 0:09:16Now the combination of rising temperature, day length,
0:09:16 > 0:09:22and phase of the moon brings them together in shoals of 10,000 or more.
0:09:22 > 0:09:26At dusk, the fish rise up towards the surface.
0:09:26 > 0:09:31The females release their eggs, the males their sperm.
0:09:33 > 0:09:35They're here to spawn.
0:09:59 > 0:10:04They do it at dusk because the fading light makes life harder for predators.
0:10:08 > 0:10:12But the snappers haven't gone entirely unnoticed.
0:10:18 > 0:10:21A whale shark.
0:10:21 > 0:10:24The length and weight of a double-decker bus.
0:10:45 > 0:10:47But he's not after the snappers.
0:10:53 > 0:10:57He hoovers up their eggs - tens of thousands in each mouthful.
0:11:12 > 0:11:17Millions of eggs are lost but millions more survive.
0:11:17 > 0:11:24The young will drift on the currents until they find a place of safety.
0:11:24 > 0:11:26A mangrove forest.
0:11:29 > 0:11:32Stretching all along the Caribbean coastline,
0:11:32 > 0:11:34these forests hold a secret.
0:11:38 > 0:11:42An extraordinary sanctuary, hidden beneath the surface.
0:12:08 > 0:12:15The roots, draped with anemones, starfish and sponges, form a living barrier.
0:12:20 > 0:12:22The bigger predators can't pass.
0:12:26 > 0:12:31And make this a safe haven, not just for snappers,
0:12:31 > 0:12:36but for the young of hundreds of species of fish.
0:12:51 > 0:12:54It's an underwater wonderland.
0:13:19 > 0:13:23These underwater forests are among the richest environments on Earth.
0:13:41 > 0:13:43By providing sheltered nurseries,
0:13:43 > 0:13:47they form a vital part of the web of life across the Caribbean.
0:13:50 > 0:13:57Sustaining life in the shallows, the reefs, and the deep sea beyond.
0:14:02 > 0:14:05But other forces affect life here.
0:14:05 > 0:14:11And one of the most powerful has its origins 3,000 miles away in Africa.
0:14:17 > 0:14:22The African sun makes the Sahara Desert one of the hottest places on Earth.
0:14:26 > 0:14:30It's May and already the temperature is nearing 40 degrees.
0:14:37 > 0:14:41The intense heat fuels powerful winds
0:14:41 > 0:14:44which blow out from the desert and west into the Atlantic.
0:14:48 > 0:14:49The trade winds.
0:14:52 > 0:14:57They first hit land 400 miles off the African coast in the Cape Verde archipelago.
0:15:04 > 0:15:08Desert islands, dominated by the wind.
0:15:17 > 0:15:21The people here have an intimate relationship with both wind and sea.
0:15:25 > 0:15:29They stitch their sails from old plastic sacks.
0:15:33 > 0:15:36Head fisherman Xavier has an instinct for the wind.
0:15:36 > 0:15:41It's all that stands between a successful trip and disaster.
0:16:21 > 0:16:23The fishermen sail far out into the Atlantic.
0:16:25 > 0:16:28Each trip can take a week or more.
0:16:31 > 0:16:33The men are dependent on wind.
0:16:35 > 0:16:37If it fails, they might not get home.
0:16:55 > 0:16:58After a successful trip, the fishermen turn for home.
0:17:01 > 0:17:06But the trade winds blow on, driving west across the ocean.
0:17:09 > 0:17:14As they move, they pick up moisture from the sea below.
0:17:14 > 0:17:21By May, the sun's heat evaporates billions of tonnes of water from the ocean surface every day.
0:17:23 > 0:17:27Clouds build and the trade winds sweep them west.
0:17:34 > 0:17:38When they finally reach the Caribbean,
0:17:38 > 0:17:40they bring a vital resource to paradise.
0:17:43 > 0:17:44Rain.
0:17:51 > 0:17:54The rain washes mud from land to sea...
0:17:58 > 0:18:03..and here, the mangrove roots slow the flow and the sediment settles.
0:18:14 > 0:18:19The mud nourishes the mangroves and the roots act as a filter,
0:18:19 > 0:18:23ensuring the waters of the Caribbean remain crystal clear.
0:18:38 > 0:18:43It's June and the sun is at its height.
0:18:46 > 0:18:47The clouds soon burn away.
0:18:55 > 0:19:01Soon, the building heat will test many of the creatures that live here to their limits.
0:19:06 > 0:19:09But for now, life is good.
0:19:13 > 0:19:18Off the Bahamas, adolescent dolphins have formed a group.
0:19:22 > 0:19:27They're getting their first spots, a sign of their new-found independence.
0:19:29 > 0:19:33Now they've been weaned, they must hunt for themselves.
0:19:36 > 0:19:39And for dolphins, hunting means teamwork.
0:19:44 > 0:19:48The group have cornered an unlucky filefish.
0:19:48 > 0:19:50But they don't plan to eat it.
0:19:54 > 0:19:59The youngsters take turns to herd the fish, communicating in intense bursts.
0:20:03 > 0:20:04More than just play,
0:20:04 > 0:20:09the youngsters are learning to coordinate their movements and work as a unit.
0:20:13 > 0:20:16Fortunately for the fish, they tire of their game.
0:20:28 > 0:20:32The ability to work together will be crucial to their survival.
0:20:42 > 0:20:47In mid-summer, the heat and light drives an explosion of plant life.
0:20:51 > 0:20:54The seagrass is growing by three centimetres a day.
0:20:59 > 0:21:00Good news for the manatee.
0:21:11 > 0:21:14But there are also thick patches of algae growing on her back.
0:21:19 > 0:21:24Conveniently, she's found a place nearby where she can get her back scrubbed.
0:21:29 > 0:21:34Alongside the reef, young parrotfish have set up a cleaning station.
0:21:34 > 0:21:36The fish get a meal and she gets cleaned.
0:21:41 > 0:21:44Now, she can go back to the serious business of eating.
0:21:49 > 0:21:53The tropical sunlight brings life to everything it touches.
0:21:58 > 0:22:03In this coastal lagoon in the Bahamas, another animal can't get enough of it.
0:22:12 > 0:22:18It may be moving slowly but this Cassiopeia jellyfish is in a hurry.
0:22:21 > 0:22:24It's on its way to a sunbathing party.
0:22:24 > 0:22:30Every day, hundreds of Cassiopeia cluster in the calmest, sunniest spots.
0:22:52 > 0:22:55These are solar powered jellyfish.
0:23:03 > 0:23:07There are algae that live just beneath their tentacles, which feed on the sun.
0:23:07 > 0:23:12They photosynthesise and the nutrients they make are food for the Cassiopeia.
0:23:23 > 0:23:26An arrangement that benefits both sides.
0:23:26 > 0:23:30The jellyfish get free food, the algae get their own mobile greenhouses -
0:23:30 > 0:23:33guaranteeing them a place in the sun.
0:23:36 > 0:23:38These jellyfish rarely need to hunt.
0:23:38 > 0:23:42With bright sunlight and algae on board, they thrive.
0:23:53 > 0:23:58And when the sun sets, they will rest, ahead of another hard day's sunbathing.
0:24:04 > 0:24:07As evening falls, the sun loses its power.
0:24:09 > 0:24:13But at this time of the year, its influence persists far into the night.
0:24:18 > 0:24:23After dark, the mangrove lagoons undergo a magical transformation.
0:24:29 > 0:24:34Something that Clifford, a fisherman from Belize, plans to take advantage of.
0:24:58 > 0:25:05All day long, an underwater life form here has been harvesting the sun's energy.
0:25:09 > 0:25:13Now, that energy will be released.
0:25:18 > 0:25:22As fish move through the water, they create a light show.
0:25:31 > 0:25:36It's not the fish that are glowing - it's something much smaller.
0:25:45 > 0:25:53Tiny single-celled creatures called dinoflagellates flourish in the rich warm waters of the mangrove lagoons.
0:26:00 > 0:26:02And when they're disturbed, they glow.
0:26:04 > 0:26:06Bioluminescence.
0:26:11 > 0:26:14A shock to warn off predators.
0:26:28 > 0:26:34They're charged up by sunlight, so the longer the days, the more intense the glow.
0:26:43 > 0:26:48The bioluminescence is so powerful that Clifford can fish in the dark.
0:27:07 > 0:27:11Further out to sea on the Caribbean's reefs,
0:27:11 > 0:27:14there's another extraordinary night-time display -
0:27:14 > 0:27:19a sign that the sun's power is now pushing the reef's ecosystem into overdrive.
0:27:34 > 0:27:38It may not look like it, but this is a coral.
0:27:38 > 0:27:42Scientists believe its glowing is an equivalent of sunscreen.
0:27:56 > 0:27:58Corals have algae living in their cells.
0:28:01 > 0:28:06As these photosynthesise, they produce food for the coral.
0:28:11 > 0:28:15But too much ultraviolet light can damage them.
0:28:15 > 0:28:17So the corals protect themselves.
0:28:22 > 0:28:26A special protein absorbs the ultraviolet light,
0:28:26 > 0:28:29and re-emits light of another colour.
0:28:31 > 0:28:35By day, the sun is too bright for this to be visible.
0:28:40 > 0:28:45But shining blue light on corals at night shows their fluorescent response.
0:29:10 > 0:29:15It's a much-needed defence mechanism when there is no escape from the midsummer sun.
0:29:38 > 0:29:43It's now August. Water temperatures have hit 29 degrees.
0:29:48 > 0:29:50Many creatures seek refuge in the shade.
0:30:00 > 0:30:05In Grand Cayman, millions of silversides gather in caves under the reef.
0:30:39 > 0:30:41There's safety in numbers...
0:30:48 > 0:30:50..but danger lurks here in the dark.
0:31:11 > 0:31:13A monster the length of a man...
0:31:15 > 0:31:16..with a ravenous appetite.
0:31:41 > 0:31:43A tarpon.
0:31:53 > 0:31:55He has explosive acceleration...
0:31:56 > 0:31:58..hitting up to 40mph.
0:32:02 > 0:32:05His cavernous jaws create a suction effect when he strikes.
0:32:09 > 0:32:10He swallows his prey whole.
0:32:18 > 0:32:22As more silversides enter the cave, more tarpon gather.
0:32:43 > 0:32:46This seasonal feast is just too good to miss.
0:33:44 > 0:33:46Heat is building in the water.
0:33:49 > 0:33:53And temperatures are rising in the dolphin community, too.
0:33:59 > 0:34:01DOLPHINS SQUEAK
0:34:04 > 0:34:07This calf is trying to stay close to his mother.
0:34:11 > 0:34:16She's in oestrus and has attracted the attention of an eager and persistent male.
0:34:19 > 0:34:22Turning belly up and blowing bubbles signals his excitement...
0:34:23 > 0:34:26..but she's not interested.
0:34:28 > 0:34:32Avoiding a single male is relatively easy,
0:34:32 > 0:34:35but groups working together are another matter entirely.
0:34:42 > 0:34:43RAPID SQUEAKING AND CLICKING
0:34:45 > 0:34:49Males from another group are on the hunt for a mate.
0:35:01 > 0:35:04They're an established team, constantly communicating.
0:35:07 > 0:35:10Their target is a lone female.
0:35:12 > 0:35:16She tries to fend them off, but they are undeterred.
0:35:16 > 0:35:17Pinning her to the seabed,
0:35:17 > 0:35:19they use their echolocation to examine her
0:35:19 > 0:35:21and see if she's ready to mate.
0:35:25 > 0:35:28The noise alerts another group of males.
0:35:28 > 0:35:30They also want access to the female.
0:35:33 > 0:35:34And they're ready to fight for it.
0:35:39 > 0:35:41COMMUNICATION INTENSIFIES
0:35:44 > 0:35:48The groups bombard each other with a deafening barrage of sound.
0:36:00 > 0:36:02The sounds normally used to stick together
0:36:02 > 0:36:04now become an intimidating weapon.
0:36:04 > 0:36:08Their head-to-head body postures and open mouths all signal aggression.
0:36:33 > 0:36:37These encounters can escalate into violence,
0:36:37 > 0:36:39but this time the intruders back off.
0:36:57 > 0:36:58The calf watches and learns.
0:37:03 > 0:37:05He's growing up in a dangerous world.
0:37:24 > 0:37:26It's the end of August.
0:37:26 > 0:37:28The sea is at its hottest.
0:37:32 > 0:37:33On the reefs,
0:37:33 > 0:37:36the rising heat is now putting life
0:37:36 > 0:37:38under serious pressure.
0:37:42 > 0:37:44Corals are very sensitive.
0:37:45 > 0:37:48If summer water temperatures rise just one degree above average...
0:37:50 > 0:37:52..it can have catastrophic effects.
0:38:07 > 0:38:11The growing heat drives the corals to eject the symbiotic algae
0:38:11 > 0:38:13that normally feed them.
0:38:19 > 0:38:20Without their algae,
0:38:20 > 0:38:23the corals lose their primary source of food
0:38:23 > 0:38:25and in just a few days
0:38:25 > 0:38:27they turn white.
0:38:38 > 0:38:41If the temperatures stay too high for too long,
0:38:41 > 0:38:42the corals will die...
0:38:49 > 0:38:52..and the animals that rely on them
0:38:52 > 0:38:53will lose their food and shelter.
0:39:01 > 0:39:05The sun, once the engine of life...
0:39:06 > 0:39:08..now threatens to destroy it.
0:39:10 > 0:39:13The whole of the tropical Atlantic
0:39:13 > 0:39:16now balances on a knife edge.
0:39:21 > 0:39:24And 3,000 miles to the east,
0:39:24 > 0:39:26a catastrophic event is building.
0:39:31 > 0:39:34On Cape Verde off the coast of Africa...
0:39:36 > 0:39:40..the hot winds from the Sahara are whipping the sea into a frenzy.
0:39:40 > 0:39:42WAVES CRASH
0:39:56 > 0:40:00The favourable conditions Xavier and his men rely upon are changing.
0:40:02 > 0:40:04Water evaporating from the warm sea
0:40:04 > 0:40:07generates turbulence and the Saharan winds.
0:40:12 > 0:40:14These are dangerous conditions.
0:40:26 > 0:40:28Xavier makes the decision to turn back.
0:40:29 > 0:40:30He knows what's coming.
0:40:36 > 0:40:38A tropical storm is brewing.
0:40:46 > 0:40:48The fishermen have packed up their boats.
0:40:50 > 0:40:53Storms blow over quickly here
0:40:53 > 0:40:57because the trade winds blow them on across the Atlantic.
0:40:57 > 0:40:58But as they travel,
0:40:58 > 0:41:01some storms grow into monsters.
0:41:04 > 0:41:05A chain reaction begins.
0:41:08 > 0:41:12The hot waters and winds combine to drive a constant cycle of convection.
0:41:14 > 0:41:16Warm air rises from the sea,
0:41:16 > 0:41:19lifting moisture to create vast banks of cloud.
0:41:21 > 0:41:24More air is sucked in below
0:41:24 > 0:41:26and a vortex begins to form.
0:41:33 > 0:41:35The storm roars across the ocean,
0:41:35 > 0:41:37growing stronger with every mile.
0:41:43 > 0:41:45When the winds reach 74mph,
0:41:45 > 0:41:48this storm finally earns a new name.
0:41:51 > 0:41:53A hurricane is born.
0:41:55 > 0:41:56An unstoppable force of nature...
0:42:00 > 0:42:02..with the Caribbean right in its path.
0:42:04 > 0:42:06The countdown to destruction has begun.
0:42:10 > 0:42:12Animals and corals,
0:42:12 > 0:42:14already close to breaking point from the rising heat,
0:42:14 > 0:42:17will soon face a violent and deadly assault.
0:42:19 > 0:42:22The warm seas that nursed them through the first part of the year
0:42:22 > 0:42:25now fuel the storm that threatens them.
0:42:30 > 0:42:32Everything is about to change.
0:42:37 > 0:42:3936 hours before impact,
0:42:39 > 0:42:42the first signs of the coming hurricane appear.
0:42:43 > 0:42:45WAVES THUNDER
0:42:53 > 0:42:56Ocean swells roll across the once tranquil sea.
0:42:59 > 0:43:01BELLS RING
0:43:01 > 0:43:03An official hurricane warning is issued.
0:43:06 > 0:43:08With 24 hours to go...
0:43:10 > 0:43:12..winds hit 35mph.
0:43:15 > 0:43:17The dolphins seek refuge in deeper water.
0:43:17 > 0:43:19SQUEAKING AND CLICKING
0:43:19 > 0:43:21Survival depends on sticking together.
0:43:23 > 0:43:26This is when their ability to communicate will really count.
0:43:34 > 0:43:36BINS CRASH
0:43:36 > 0:43:38On land, those unable to evacuate
0:43:38 > 0:43:40must batten down the hatches and wait.
0:43:47 > 0:43:4912 hours before landfall,
0:43:49 > 0:43:53huge walls of thunderstorms bring intense bands of rain.
0:43:53 > 0:43:54GLASS SHATTERS
0:43:56 > 0:43:58Winds now gust to over 70mph.
0:44:00 > 0:44:02They batter the mangroves.
0:44:05 > 0:44:08A rising surge of water driven on shore by the wind...
0:44:10 > 0:44:12..engulfs the coastline.
0:44:18 > 0:44:21The sea is an impenetrable murk.
0:44:24 > 0:44:28At their peak, winds can hit 120mph.
0:44:32 > 0:44:35The relentless power of the sun
0:44:35 > 0:44:37has turned paradise into hell.
0:44:49 > 0:44:52SILENCE
0:45:10 > 0:45:13Hurricanes are one of the deadliest natural forces on the planet.
0:45:16 > 0:45:19On land, they destroy property...
0:45:20 > 0:45:22..but people can seek refuge.
0:45:30 > 0:45:32Animals at sea have no protection at all.
0:45:37 > 0:45:40Hurricanes can break up dolphin groups,
0:45:40 > 0:45:42leaving stragglers lost and vulnerable.
0:45:44 > 0:45:47Alone, a young calf is easy prey for sharks.
0:45:54 > 0:45:57The mangrove forests bore the full brunt of the storm.
0:46:02 > 0:46:05Their life-giving sediments are violently churned.
0:46:11 > 0:46:14The turbid water appears lifeless.
0:46:27 > 0:46:29MANATEE SNORTS
0:46:29 > 0:46:33But the roots make the mangroves a safe haven.
0:46:43 > 0:46:47Manatees head deep into the mangroves during hurricanes,
0:46:47 > 0:46:49knowing they will find safety.
0:47:25 > 0:47:27The trees act like a living crumple zone.
0:47:29 > 0:47:33The roots dissipate the destructive energy better than any seawall.
0:47:34 > 0:47:37They calm the waves and tame the surge.
0:47:38 > 0:47:41The mangroves are the Caribbean's storm shelter.
0:47:47 > 0:47:50The roots protect the precious fish nurseries
0:47:50 > 0:47:52and in the aftermath,
0:47:52 > 0:47:54they slow the moving water,
0:47:54 > 0:47:57allowing sediments to settle and the waters to clear.
0:48:03 > 0:48:07The mangroves don't just protect against hurricanes.
0:48:07 > 0:48:09They can also benefit from them.
0:48:13 > 0:48:17The storm surge disperses mangrove seedlings far and wide
0:48:17 > 0:48:20and these will take root in clearings in the forest.
0:48:23 > 0:48:27A sanctuary for the tropical Atlantic will continue to grow.
0:48:39 > 0:48:40Out on the reef,
0:48:40 > 0:48:44hurricanes take the energy out of the overloaded system.
0:48:44 > 0:48:46Some corals are damaged,
0:48:46 > 0:48:49but the torrential rain cools the waters.
0:48:51 > 0:48:54The corals will take back their algae,
0:48:54 > 0:48:56the reef will thrive again.
0:49:07 > 0:49:09Off the Bahamas...
0:49:10 > 0:49:14..hurricanes have been known to devastate dolphin groups.
0:49:20 > 0:49:23The only way a stranded calf will survive...
0:49:24 > 0:49:26..is to reunite with a group.
0:49:33 > 0:49:35DOLPHINS SQUEAK
0:49:38 > 0:49:40Nature has a way of bouncing back.
0:49:43 > 0:49:45In groups that do lose calves,
0:49:45 > 0:49:48scientists have found that females come back into oestrus
0:49:48 > 0:49:50more quickly than usual.
0:49:52 > 0:49:54The result is a baby-boom.
0:50:02 > 0:50:05It's time for the group to reinforce all bonds.
0:50:11 > 0:50:13CLICKING AND SQUEAKING
0:50:13 > 0:50:16Life in the tropical Atlantic resumes where it left off.
0:50:35 > 0:50:38For now, all is calm in paradise.
0:50:40 > 0:50:42But soon the heat will build once again.
0:50:47 > 0:50:50The sun creates opportunities for life,
0:50:50 > 0:50:53yet it can also bring destruction.
0:50:53 > 0:50:56All living things here must learn to survive both heaven and hell.
0:50:58 > 0:51:02The vast opposing forces of this extraordinary ocean...
0:51:02 > 0:51:04the Atlantic.
0:51:16 > 0:51:20MUSIC: Mr Brown (Blend Mishkin Remix) by Dirty Dubsters featuring Bass Nacho
0:51:20 > 0:51:23The warm sundrenched shallows of the Caribbean Sea
0:51:23 > 0:51:25are teeming with life.
0:51:29 > 0:51:32The Atlantic team spent more than 300 hours underwater,
0:51:32 > 0:51:34all across the Caribbean
0:51:34 > 0:51:36and met some very special animals.
0:51:38 > 0:51:41From the tranquil lagoons of Belize...
0:51:45 > 0:51:47..to the sandbanks of the Bahamas...
0:51:49 > 0:51:52..and the spectacular caves of the Cayman Islands.
0:52:09 > 0:52:12But to reveal some amazing new discoveries about corals,
0:52:12 > 0:52:14the team had to turn to science
0:52:14 > 0:52:16for a new way of looking at the world.
0:52:19 > 0:52:22Scientists have recently discovered that some corals
0:52:22 > 0:52:24appear to have a natural sunscreen.
0:52:26 > 0:52:29And to reveal this in its full technicolor glory,
0:52:29 > 0:52:32the team are to leave their usual habitat.
0:52:38 > 0:52:43In Miami, the only US city actually built on a coral reef,
0:52:43 > 0:52:47there's one place where corals are always in the spotlight.
0:52:58 > 0:53:01Colin Foord is a marine biologist and cameraman
0:53:01 > 0:53:03with a passion for corals.
0:53:03 > 0:53:05Just the man to help producer Renee Godfrey
0:53:05 > 0:53:08get the unique images of these amazing animals
0:53:08 > 0:53:09that she's hoping for.
0:53:10 > 0:53:14And in your photography and filmmaking of these corals,
0:53:14 > 0:53:17- you're trying to take people, really, into a...- Yeah...
0:53:17 > 0:53:20- ..a macro world. - ..into a macro universe.
0:53:25 > 0:53:27Coral reefs are built by colonies of tiny animals.
0:53:29 > 0:53:33Colin studies them with lenses that can magnify up to 200 times.
0:53:39 > 0:53:42He rescues corals which are threatened by dredging
0:53:42 > 0:53:44in Miami's waterways
0:53:44 > 0:53:47- and relocates them to protected areas on the city's outskirts. - TAPPING
0:53:57 > 0:53:59Colin takes small samples of the city's corals
0:53:59 > 0:54:03to study how well they cope with pollution and rising temperatures.
0:54:06 > 0:54:08Some of his work involves a combination
0:54:08 > 0:54:10of science and photography.
0:54:30 > 0:54:33Corals are mysterious animals, they're mysterious creatures.
0:54:33 > 0:54:35I see them as the most alien
0:54:35 > 0:54:39and cosmic of the organisms on the planet
0:54:39 > 0:54:41and I find that to be incredibly intriguing.
0:54:47 > 0:54:50Colin uses blue light and zoom lenses with special filters
0:54:50 > 0:54:54to reveal something that is barely visible to the naked eye
0:54:54 > 0:54:56and impossible to film in daylight.
0:54:58 > 0:55:02Now Renee is able to see exactly what she came looking for.
0:55:09 > 0:55:11Under the blue light, the corals fluoresce.
0:55:16 > 0:55:20Pigments in the coral absorb the ultraviolet component of the blue light
0:55:20 > 0:55:23and re-emit it in different colours.
0:55:23 > 0:55:26In the wild, it's thought this adaptation protects the coral
0:55:26 > 0:55:28from the sun's damaging ultraviolet rays.
0:55:31 > 0:55:32Oh!
0:55:32 > 0:55:34- They really have opened up, haven't they?- Hm.
0:55:36 > 0:55:41The corals put out tiny tentacles to catch food from the water.
0:55:41 > 0:55:43And with time-lapse photography,
0:55:43 > 0:55:45the crew make the images even more revealing.
0:55:54 > 0:55:58The coral is almost working on a different timescale than the human timescale.
0:55:58 > 0:56:00Everything is much slower for a coral.
0:56:00 > 0:56:03Working in a laboratory, we can film for a long period of time
0:56:03 > 0:56:05and then speed up,
0:56:05 > 0:56:07so you start to see the way that the coral...
0:56:07 > 0:56:09You can see the mouth eating and moving.
0:56:10 > 0:56:13You look at them and they don't look like they're very animate,
0:56:13 > 0:56:16but once you stop and observe them,
0:56:16 > 0:56:19you realise just how alive corals are.
0:56:21 > 0:56:23They're just the most amazing colours.
0:56:23 > 0:56:25It's really...
0:56:25 > 0:56:27- Wow!- Oh!
0:56:32 > 0:56:35Renee has got the shots she came for,
0:56:35 > 0:56:39revealing the coral's extraordinary adaptation for coping with the tropical sun.
0:56:42 > 0:56:44But for Colin, filming these beautiful images
0:56:44 > 0:56:46is part of a wider mission.
0:56:53 > 0:56:57- You're showing corals in an incredibly artistic way.- Yes.
0:56:59 > 0:57:03On the one hand, we just want the corals to be able to present themselves.
0:57:03 > 0:57:06Corals are these living art forms.
0:57:06 > 0:57:10The natural beauty of these corals can sell themselves to the public.
0:57:10 > 0:57:12As to, "Why should we care about the coral reefs?"
0:57:12 > 0:57:15Perhaps you've never been able to get so close to a coral.
0:57:15 > 0:57:17Well, look at these beautiful organisms.
0:57:30 > 0:57:33Specialist photography is helping us to learn more and more
0:57:33 > 0:57:35about these extraordinary life forms.
0:57:44 > 0:57:47With passionate people like Colin on their side,
0:57:47 > 0:57:49these cosmic corals of the Atlantic
0:57:49 > 0:57:51may have a bright future.
0:57:51 > 0:57:54There's no end to what his camera might reveal.