0:00:28 > 0:00:31Away from all land.
0:00:31 > 0:00:34The ocean.
0:00:34 > 0:00:42It covers more than half the surface of our planet and yet, for the most part, it is beyond our reach.
0:00:45 > 0:00:50Much of it is virtually empty,
0:00:50 > 0:00:52a watery desert.
0:00:57 > 0:01:03All life that is here is locked in a constant search to find food.
0:01:05 > 0:01:10A struggle to conserve precious energy in the open ocean.
0:01:30 > 0:01:33The biggest of all fish.
0:01:33 > 0:01:3730 tonnes in weight, 12 metres long -
0:01:37 > 0:01:39a whale shark.
0:01:41 > 0:01:47Its huge bulk is sustained by near-microscopic creatures of the sea -
0:01:47 > 0:01:49plankton.
0:01:51 > 0:01:58Whale sharks cruise on regular, habitual routes between the best feeding grounds.
0:02:02 > 0:02:08In February, that takes them to the surface waters far from the coast of Venezuela.
0:02:11 > 0:02:15Others are already here.
0:02:15 > 0:02:20Bait fish have come for the same reason - to feed on the plankton.
0:02:20 > 0:02:24The whale shark has timed its arrival exactly right.
0:02:26 > 0:02:30Oddly, the tiny fish swarm around it.
0:02:37 > 0:02:40They're using it as a shield.
0:02:44 > 0:02:48Other predatory fish are lurking nearby.
0:02:50 > 0:02:53Yellowfin tuna.
0:02:53 > 0:02:56They seem wary of the giant.
0:03:02 > 0:03:06The shark dives, as if to escape from such overcrowding.
0:03:11 > 0:03:16Now the tuna have a chance to attack the unprotected baitfish.
0:03:27 > 0:03:31But then, back comes the giant.
0:03:38 > 0:03:42It has taken a vast mouthful of the baitfish itself.
0:03:42 > 0:03:47Plankton, it seems, is not the only food for a whale shark.
0:03:58 > 0:04:01Both shark and tuna feast together.
0:04:16 > 0:04:19But the tuna must beware.
0:04:22 > 0:04:27Even they can end up in the whale shark's stomach.
0:04:35 > 0:04:42Predators here must grab what they can, when they can, for such events do not last long.
0:04:45 > 0:04:51The dense shoals on which so many depend, gather only when water conditions are perfect.
0:05:05 > 0:05:12Many predators spend much of their time cruising the open ocean, endlessly searching.
0:05:16 > 0:05:21Plankton-feeding rays do so, gliding with minimum effort.
0:05:36 > 0:05:39The oceanic white tip shark.
0:05:41 > 0:05:44Another energy-efficient traveller.
0:05:46 > 0:05:52It specialises in locating prey in the emptiest areas of the open ocean,
0:05:52 > 0:05:55patrolling the top 100 metres of water.
0:06:03 > 0:06:08Taste in water is the equivalent of smell in the air.
0:06:08 > 0:06:14An oceanic white tip is able to detect even the faintest trace.
0:06:17 > 0:06:20Small pilot fish swim with it.
0:06:20 > 0:06:23The shark can find prey far more easily than they can
0:06:23 > 0:06:27and they'll be able to collect the scraps from its meals.
0:06:31 > 0:06:35Its long fixed pectoral fins
0:06:35 > 0:06:40enable it to soar through the water with the least expenditure of energy.
0:06:45 > 0:06:50This shark has found a school of rainbow runners.
0:06:50 > 0:06:52It would eat one, given the chance.
0:06:52 > 0:06:57But rainbow runners are swift and agile and not easily caught.
0:06:59 > 0:07:03So it bides its time.
0:07:03 > 0:07:08There's a chance that, eventually, it may spot a weakened fish that's catchable.
0:07:12 > 0:07:13The hunter,
0:07:13 > 0:07:15endlessly waiting.
0:07:26 > 0:07:29Excitement far from land.
0:07:38 > 0:07:41A school of dolphin, 500-strong.
0:07:55 > 0:08:01They've sensed there's food around and they're racing to catch up with it.
0:08:09 > 0:08:14The news has spread - now a number of schools are on their way.
0:08:28 > 0:08:34They're heading towards the Azores, volcanic islands 1,000 miles west of Portugal.
0:08:42 > 0:08:47The dolphins scan the water ahead with their sonar.
0:08:47 > 0:08:49They're close to their target.
0:08:54 > 0:08:58CLICKING
0:08:58 > 0:09:02This is it - scad mackerel.
0:09:05 > 0:09:09It's difficult for a single dolphin to catch the fish.
0:09:09 > 0:09:14To avoid wasting energy, they work as a group.
0:09:21 > 0:09:25They drive the fish upwards, trapping them against the surface.
0:09:27 > 0:09:31And there, other predators await them.
0:09:34 > 0:09:36Corey shearwaters.
0:09:36 > 0:09:41They're waiting for the dolphin to drive the prey closer to the surface.
0:09:51 > 0:09:57Now the shearwaters can dive down on them, descending to twenty metres or more.
0:10:00 > 0:10:04And the dolphins block the bait ball's retreat.
0:10:34 > 0:10:38The dolphins leave as soon as they've had their fill.
0:10:43 > 0:10:48And at last the mackerel sink below the diving range of the birds.
0:11:11 > 0:11:17As the sun disappears, a profound change takes place in the ocean.
0:11:18 > 0:11:22Deep-water plankton start to rise from the depths.
0:11:22 > 0:11:27And another hungry army prepares to receive it.
0:11:50 > 0:11:53Every night, wherever conditions are right,
0:11:53 > 0:12:00countless millions of creatures from the deep migrate to the surface, seeking food.
0:12:09 > 0:12:16A baby sailfish, 15 centimetres long, snaps up everything in its path.
0:12:16 > 0:12:23In three years' time, it'll be one of the ocean's most formidable hunters weighing 60 kilos.
0:12:23 > 0:12:28Just now, however, it's very vulnerable.
0:13:08 > 0:13:11These manta rays are giants.
0:13:11 > 0:13:16Eight metres across and weighing over two tonnes.
0:13:19 > 0:13:27The blade-like projections on either side of the head help to steer plankton into the manta's mouth.
0:13:45 > 0:13:50Dawn returns and the plankton sinks back into the depths.
0:13:51 > 0:13:56If we are to follow, we must use a submarine.
0:14:00 > 0:14:06As we descend into the darkness, the pressure builds, the temperature falls.
0:14:10 > 0:14:14Below 500 metres, new mysterious animals appear.
0:14:20 > 0:14:26Their bizarre shapes help them to remain suspended in the dark space.
0:14:29 > 0:14:34Some resemble creatures familiar from shallower waters.
0:14:42 > 0:14:45Others defy classification.
0:14:50 > 0:14:56All around, organic particles drift downwards -
0:14:57 > 0:15:03"marine snow", detritus from the creatures swarming in the sunlit waters above.
0:15:05 > 0:15:11The snow is food for many animals here like the sea spider...
0:15:11 > 0:15:14a small relative of shrimps and crabs.
0:15:25 > 0:15:32Those strange leg-like appendages are feathered, to stop it from sinking.
0:15:34 > 0:15:41They can also enmesh marine snow, which it wipes carefully into its jaws.
0:15:56 > 0:16:01A sawtooth eel hangs upright and motionless.
0:16:04 > 0:16:09Gazing ever upwards, it watches for prey silhouetted
0:16:09 > 0:16:13against the faint glimmerings of light from the surface.
0:16:18 > 0:16:24Days may pass before prey swims close enough for it to strike.
0:16:28 > 0:16:33Farther down still, the blackness is complete.
0:16:33 > 0:16:38No vestige of sunlight can penetrate as far as this.
0:16:41 > 0:16:48Food is very scarce and nothing can afford to waste any energy.
0:16:50 > 0:16:55A dumbo octopus simply flaps a fin.
0:16:55 > 0:17:00No need for the jet propulsion used by its shallow-water relatives above.
0:17:30 > 0:17:36The weirdest in this world of the strange - vampyroteuthis,
0:17:36 > 0:17:39the "vampire squid from hell".
0:17:43 > 0:17:48Disturb it, and it only retreats a little distance.
0:17:52 > 0:17:56Go after it, and it has a special defence.
0:17:58 > 0:18:04To see what it does, you must switch off the lights.
0:18:05 > 0:18:09The vampire squid has lights of its own.
0:18:12 > 0:18:19Bioluminescent bacteria shine from pockets on its arms, to confuse its predators.
0:18:19 > 0:18:21Are those eyes?
0:18:26 > 0:18:29In fact they're spots at the end of its mantle.
0:18:29 > 0:18:33A bite there would leave the head unscathed.
0:18:33 > 0:18:37The threat diminishes
0:18:37 > 0:18:41and vampyroteuthis disappears into the blackness.
0:18:56 > 0:18:59At last, the sea floor.
0:18:59 > 0:19:02Over two miles down.
0:19:02 > 0:19:07The pressure here is 300 times that at the surface.
0:19:07 > 0:19:13It takes several months for marine snow to drift down as far as this.
0:19:17 > 0:19:24As you travel away from the rocky margins of the continents, an immense plain stretches ahead.
0:19:27 > 0:19:30It extends for thousands of miles,
0:19:30 > 0:19:32gradually sinking downwards.
0:19:39 > 0:19:43There are faint trails in the ooze...
0:19:43 > 0:19:46signs that even here, there is life.
0:19:53 > 0:19:57These are what made some of them.
0:19:57 > 0:20:01Sea urchins sifting the accumulating drifts.
0:20:04 > 0:20:12Shrimps, standing on elegant tip-toe, fastidiously select the particles that appeal to them.
0:20:19 > 0:20:26But in the deep sea, as everywhere else, if there are grazers, there are hunters.
0:20:35 > 0:20:37A monkfish.
0:20:37 > 0:20:42Almost indistinguishable from the sand on which it lies.
0:20:47 > 0:20:53Why waste energy chasing around, if you can attract prey towards you with a lure?
0:21:10 > 0:21:14Maybe that one was a bit big.
0:21:16 > 0:21:23The monkfish can wait - for days if necessary - until the right-sized meal turns up.
0:21:26 > 0:21:32Scavengers, on the other hand, have to move around to find their food.
0:21:34 > 0:21:38Crabs can detect the faintest of tastes in the water
0:21:38 > 0:21:43and that helps them locate the latest body to drift down from above.
0:21:44 > 0:21:48Eels are already feeding on the corpse.
0:21:54 > 0:21:59Isopods, like giant marine woodlice a third of a metre long,
0:21:59 > 0:22:02are ripping into the rotting flesh.
0:22:03 > 0:22:06Over the next few hours, there'll be frenzied competition
0:22:06 > 0:22:10between scavengers of all kinds to grab a share.
0:22:39 > 0:22:44Just occasionally there is a gigantic bonanza.
0:22:52 > 0:22:56The remains of a sperm whale.
0:22:56 > 0:22:59It died five months or so ago.
0:22:59 > 0:23:04There's little left but fatty blubber clinging to its bones.
0:23:06 > 0:23:13Its flesh has nourished life for miles around, but now the feast is almost over.
0:23:17 > 0:23:24Spider crabs a metre across still pick at the last putrid remains.
0:23:31 > 0:23:37A few weeks more, and nothing will be left but bare bones.
0:23:37 > 0:23:42The crabs will have to fast until the next carcass drifts down.
0:23:49 > 0:23:54But not all food comes from the sunlit world above.
0:23:54 > 0:24:00The floor of the Atlantic Ocean is split in two by an immense volcanic mountain chain
0:24:00 > 0:24:06that winds unbroken for 45,000 miles around the globe.
0:24:10 > 0:24:15In places, it's riven by great fissures from which superheated water
0:24:15 > 0:24:21loaded with dissolved minerals, blasts into the icy depths.
0:24:31 > 0:24:36Clouds of sulphides solidify into towering chimneys
0:24:36 > 0:24:39as tall as a three-storey house.
0:24:43 > 0:24:47At 400 degrees, this scalding cocktail of chemicals
0:24:47 > 0:24:51would be lethally toxic to most forms of life.
0:24:53 > 0:24:58But astoundingly, a particular kind of bacteria thrives here.
0:24:58 > 0:25:03And feeding on the bacteria, vast numbers of shrimps.
0:25:13 > 0:25:17So, beyond the farthest reach of the sun's power,
0:25:17 > 0:25:20a rich, independent community exists
0:25:20 > 0:25:24that draws all its energy directly from the earth's molten core.
0:25:39 > 0:25:45On the other side of the planet, in the western Pacific bordering Japan,
0:25:45 > 0:25:47the Dragon Chimneys.
0:25:47 > 0:25:52Another series of hot vents erupting in the darkness.
0:25:59 > 0:26:05Here, more but different bacteria thrive in a similar way.
0:26:10 > 0:26:13And here, too, more crustaceans,
0:26:13 > 0:26:17quite different species from those around the hot vents in the Atlantic.
0:26:24 > 0:26:28These are squat lobsters, clad in furry armour,
0:26:28 > 0:26:32jostling with one another beside the jets of superheated water
0:26:32 > 0:26:36for the best places from which to graze on bacteria.
0:26:42 > 0:26:48These vents too, like those in the Atlantic, are isolated oases,
0:26:48 > 0:26:52so widely separated that each community is unique.
0:27:03 > 0:27:06Cross to the other side of the Pacific,
0:27:06 > 0:27:09to the deep near the Galapagos Islands,
0:27:09 > 0:27:13and there are yet other fissures venting superheated water.
0:27:19 > 0:27:24One and a half miles down, at a site known as Nine North,
0:27:24 > 0:27:29towering chimneys support a spectacular display of giant tube-worms.
0:27:35 > 0:27:38These vents give off so much energy
0:27:38 > 0:27:42that some of the worms reach three metres in length.
0:27:42 > 0:27:46They're the fastest-growing marine invertebrates known.
0:27:50 > 0:27:57All told, over 50 different species have so far been found living here.
0:28:01 > 0:28:06The inhabitants of these bustling communities may grow at speed,
0:28:06 > 0:28:09but their existence can also be short,
0:28:09 > 0:28:13for the vents do not erupt indefinitely.
0:28:13 > 0:28:17Suddenly, unpredictably, they may become inactive.
0:28:21 > 0:28:25Nine months have passed at Nine North.
0:28:25 > 0:28:29What were only recently chimneys teeming with life
0:28:29 > 0:28:34have turned into cold, sterile mineral monuments.
0:28:37 > 0:28:44Some eddy, deep in the earth's crust, diverted the volcanic energy elsewhere
0:28:44 > 0:28:48and an entire micro-world was extinguished.
0:28:56 > 0:29:02In places, volcanoes have erupted to build great submarine mountains.
0:29:02 > 0:29:07There are thought to be around 30,000 such volcanoes -
0:29:07 > 0:29:12some, measured from the sea floor, are taller than Everest.
0:29:17 > 0:29:23Sheer cliffs soaring to drowned volcanic peaks.
0:29:34 > 0:29:38Powerful currents sweep up the mountain's flanks,
0:29:38 > 0:29:42transporting nutrients from deep water towards the summits.
0:29:45 > 0:29:48The hard rock provides excellent anchorage
0:29:48 > 0:29:52for communities of great variety and stunning colour.
0:29:54 > 0:30:00Soft corals, several metres across, collect the "marine snow"
0:30:00 > 0:30:03as it drifts past.
0:30:04 > 0:30:08Whip corals stretch out into the current.
0:30:10 > 0:30:15Giant sponges filter nourishment from the cold water.
0:30:29 > 0:30:35A richly varied community flourishes here, sustained by the nutrients
0:30:35 > 0:30:39and detritus in the icy currents that flow around the peak.
0:30:44 > 0:30:48Yet it is all blossoming on an extinct volcano
0:30:48 > 0:30:51a mile below the reach of the sun.
0:31:16 > 0:31:21A nautilus. It spends its days hiding 400 metres down,
0:31:21 > 0:31:26but as night falls, it ascends up to the reefs to look for food.
0:31:31 > 0:31:36Its graceful shell contains gas-filled flotation chambers
0:31:36 > 0:31:38that control its depth.
0:31:40 > 0:31:45It's powered by a jet of water squirting from a siphon.
0:31:47 > 0:31:53But it travels shell-first so it can't see exactly where it's going.
0:31:58 > 0:32:02Its nearest living relatives are squid and octopus
0:32:02 > 0:32:07which, over evolutionary time, have both lost their shells.
0:32:07 > 0:32:12And the octopus has become one of the nautilus's major predators.
0:32:12 > 0:32:15It's a master of disguise.
0:32:20 > 0:32:24The nautilus keeps well clear of them.
0:32:25 > 0:32:31Its small tentacles carry highly developed chemical sensors
0:32:31 > 0:32:35which can detect traces of both predators and prey.
0:32:40 > 0:32:46It uses its water jet to dig in the sand.
0:32:49 > 0:32:53Because it devotes so little energy to swimming,
0:32:53 > 0:32:55it only needs a meal once a month.
0:33:00 > 0:33:01Got something.
0:33:03 > 0:33:04And just as well.
0:33:04 > 0:33:10Dawn is approaching and it has to puff its way back to deeper waters.
0:33:31 > 0:33:3730 miles away, shoals of squid are jetting upwards towards the surface.
0:33:38 > 0:33:43By night, they seek small fish among the plankton, but they're cautious.
0:33:46 > 0:33:48ANIMALS SQUEAK
0:33:50 > 0:33:53Pacific spotted dolphin.
0:33:57 > 0:33:59They're guided by their sonar.
0:33:59 > 0:34:02THEY SQUEAK
0:34:04 > 0:34:08The dolphin, as so often are working as a team,
0:34:08 > 0:34:12synchronising their attacks to confuse their prey.
0:34:12 > 0:34:14THEY SQUEAK
0:34:30 > 0:34:36As dawn approaches, squid and fish and plankton retreat downwards
0:34:36 > 0:34:38to shelter in the darkness.
0:35:03 > 0:35:06Some of these isolated volcanoes rise
0:35:06 > 0:35:12as much as 9,000 metres from the sea floor, reaching close to the surface.
0:35:15 > 0:35:20Around these peaks, invigorated by daily sunshine,
0:35:20 > 0:35:25marine life flourishes in spectacular abundance.
0:35:33 > 0:35:39Fish crowd here because the volcano forces nutrients to the surface,
0:35:39 > 0:35:42encouraging the plankton to bloom.
0:36:01 > 0:36:05An oceanic wanderer, a mola mola, stops by
0:36:05 > 0:36:09to be cleaned by reef fish at the seamount edge.
0:36:16 > 0:36:21Butterfly fish pluck string-like parasites from its flanks.
0:36:28 > 0:36:33The huge fish lives on jellyfish over 1,000 metres down
0:36:33 > 0:36:36where the water is 20 degrees colder.
0:36:36 > 0:36:41So a brush-up near the surface allows it to warm up
0:36:41 > 0:36:44before making more deep-water forays.
0:36:51 > 0:36:58The summit of this volcanic mountain rises above the surface of the sea.
0:36:59 > 0:37:01It's Ascension Island,
0:37:01 > 0:37:04800 miles from any other land,
0:37:04 > 0:37:09a welcome, vital haven for long-distance travellers.
0:37:14 > 0:37:18Frigate birds spend months continuously airborne at sea.
0:37:18 > 0:37:24But at nesting time, they come to Ascension from all over the ocean.
0:37:28 > 0:37:32The island's barren slopes of volcanic ash and lava
0:37:32 > 0:37:36might seem to offer perfectly good sites for a nest.
0:37:38 > 0:37:42But the frigates choose an even more isolated site -
0:37:44 > 0:37:49Boatswainbird Island, a lonely pillar just off Ascension's coast.
0:37:57 > 0:38:03Frigates are the world's lightest bird relative to their wingspan
0:38:03 > 0:38:07and they can soar for weeks on end with minimal effort.
0:38:10 > 0:38:13They seem much more at home in the skies
0:38:13 > 0:38:18than in a crowded colony on land, but nest they must.
0:38:20 > 0:38:25They come from all over the Atlantic to this, their only colony.
0:38:28 > 0:38:30There are boobies here too.
0:38:35 > 0:38:42To raise their young, seabirds worldwide seek such remote islands.
0:38:51 > 0:38:56Swimmers also come to Ascension to breed.
0:38:57 > 0:39:01A female green turtle approaches the coast.
0:39:03 > 0:39:07She's not eaten once in two months.
0:39:09 > 0:39:13She may have travelled 1,000 miles from her feeding grounds -
0:39:13 > 0:39:16the greatest journey of her kind.
0:39:23 > 0:39:26Many others are here too, resting on the sandy sea floor,
0:39:26 > 0:39:32awaiting the darkness of night when it'll be safer to visit the beaches.
0:39:38 > 0:39:42Eggs that were laid a few weeks ago at the start of the season
0:39:42 > 0:39:44are beginning to hatch.
0:39:57 > 0:40:00Most hatchings happen at night.
0:40:00 > 0:40:04Now in the light of day, the young are extremely vulnerable.
0:40:11 > 0:40:14They must get to the sea as soon as possible.
0:40:16 > 0:40:19But their trials have only just begun.
0:40:32 > 0:40:36Many will drown in the pounding waves.
0:41:00 > 0:41:05During the next 20 years, the vast majority will inevitably die.
0:41:05 > 0:41:10Those that survive will eventually, as their mothers did before them,
0:41:10 > 0:41:14return to the very same beach where they were hatched.
0:41:16 > 0:41:21How they find their way back across thousands of miles of open ocean,
0:41:21 > 0:41:23we still have no idea.
0:41:32 > 0:41:34A frigate soars.
0:41:35 > 0:41:41Somewhere beneath the surface below, there is the food it must have.
0:41:42 > 0:41:43But where?
0:41:45 > 0:41:48Those that fly above the ocean
0:41:48 > 0:41:52must be able to read the signs of fresh supplies or perish.
0:41:55 > 0:42:01100 miles from the Mexican coast, and keen eyes have spotted movement.
0:42:06 > 0:42:11Sailfish, three metres long, are closing in on prey.
0:42:17 > 0:42:22They will only use just enough energy to make their kill,
0:42:22 > 0:42:24never wasting a fin stroke.
0:42:29 > 0:42:34Nearly 100 sailfish have surrounded a single school of baitfish.
0:42:34 > 0:42:39It's very rare to see so many of these hunters in one place.
0:42:41 > 0:42:46To herd their prey, the predators raise their huge dorsal fins.
0:43:03 > 0:43:08A mistimed strike by one sailfish could fatally damage another.
0:43:08 > 0:43:11But each continually changes its colour,
0:43:11 > 0:43:13from blue, to striped, to black.
0:43:13 > 0:43:17That warns its companions of its intentions
0:43:17 > 0:43:19and also confuses the prey.
0:43:22 > 0:43:25As the shoal is driven nearer the surface,
0:43:25 > 0:43:27it comes within the range of the seabirds.
0:43:42 > 0:43:47Out here in the open ocean, there is nowhere for the baitfish to hide.
0:44:29 > 0:44:33Sailfish live a high-octane life.
0:44:34 > 0:44:37To survive, they must find prey daily
0:44:37 > 0:44:42so their entire existence will be spent on the move.
0:44:53 > 0:44:59Over 90% of the living space for life on our planet is in the oceans.
0:45:01 > 0:45:07Home to the biggest animal that exists or has ever existed.
0:45:08 > 0:45:11The blue whale.
0:45:17 > 0:45:21Some weigh nearly 200 tonnes,
0:45:22 > 0:45:25twice the size of the largest dinosaur.
0:45:29 > 0:45:35Despite their great size, we still have little idea of where they travel
0:45:35 > 0:45:40in the vast oceans and none at all of where they go to breed.
0:46:09 > 0:46:14The largest animal on Earth feeds almost exclusively
0:46:14 > 0:46:20on one of the smallest - krill, shrimp-like crustaceans.
0:46:21 > 0:46:25They take many tons of water into their ballooning throats
0:46:25 > 0:46:30in a single gulp and sieve out what it contains.
0:46:37 > 0:46:43Every day, each one swallows some four million krill.
0:46:45 > 0:46:51Such gargantuan harvests depend on the continuing fertility
0:46:51 > 0:46:53of the oceans.
0:46:54 > 0:46:59But global changes now threaten the great blooms of plankton
0:46:59 > 0:47:02on which the whales depend.
0:47:04 > 0:47:11Once - and not so long ago - 300,000 blue whales roamed the oceans.
0:47:12 > 0:47:16Now less than 3% of that number remains.
0:47:20 > 0:47:24Our planet is still full of wonders.
0:47:24 > 0:47:31As we explore them, so we gain not only understanding, but power.
0:47:32 > 0:47:38It's not just the future of the whale that today lies in our hands,
0:47:38 > 0:47:43but the survival of the natural world in all parts of the living planet.
0:47:45 > 0:47:49We can now destroy or we can cherish.
0:47:52 > 0:47:55The choice is ours.
0:48:21 > 0:48:24For the Planet Earth team, just finding their subjects
0:48:24 > 0:48:29in the vast, empty spaces of the open ocean was often difficult enough.
0:48:29 > 0:48:33But one of their greatest challenges was to find the increasingly rare
0:48:33 > 0:48:38oceanic white tip shark and film this fearsome predator
0:48:38 > 0:48:41in blue water without the safety of a shark cage.
0:48:49 > 0:48:50The Bahamas in winter,
0:48:50 > 0:48:55and the underwater team prepares to film rare close-up images
0:48:55 > 0:48:59of oceanic white tips in their natural surroundings.
0:48:59 > 0:49:02Cameraman Rick Rosenthal has been working in the open ocean
0:49:02 > 0:49:06for over 30 years and has filmed these sharks before.
0:49:06 > 0:49:09It came up, roaring right up to the Zodiac and I was...
0:49:09 > 0:49:11the mouth was full open.
0:49:11 > 0:49:16To help him, he's trusting his life to the latest in wetsuit camouflage.
0:49:16 > 0:49:19The new Rick Rosenthal,
0:49:19 > 0:49:25I'm going the pelagic jellyfish look, to kind of get lost in the big world out there.
0:49:25 > 0:49:28Whatever we can do to get an edge,
0:49:28 > 0:49:31anything to get close to the animals.
0:49:35 > 0:49:39Also on board is cameraman Doug Anderson.
0:49:39 > 0:49:42He's never encountered an oceanic white tip before,
0:49:42 > 0:49:45but he does have a view on what they'll be like.
0:49:45 > 0:49:48I roughly think of them like little dogs,
0:49:49 > 0:49:54and some little dogs are nice little dogs and some little dogs are nasty little dogs.
0:49:54 > 0:49:58Whatever - when you're in the water, you have to make your presence felt
0:49:58 > 0:50:01and try and judge the situation to the best of your ability.
0:50:03 > 0:50:05Unlike the more familiar reef sharks,
0:50:05 > 0:50:09oceanic white tips are true ocean wanderers.
0:50:09 > 0:50:12Once they were abundant, but fishing for shark fins
0:50:12 > 0:50:17has devastated their numbers, making them far more difficult to find.
0:50:23 > 0:50:29As they prepared to dive, they had no way of knowing what lay in wait below.
0:50:44 > 0:50:49It was soon clear that regardless of being nice or nasty,
0:50:49 > 0:50:53Doug's "little dogs" were also somewhat camera-shy.
0:50:53 > 0:50:54Nothing.
0:50:56 > 0:50:58Fishless.
0:50:58 > 0:51:02As with most dives in the open ocean, seeing nothing is normal,
0:51:02 > 0:51:06so Rick and Doug persisted in their search.
0:51:06 > 0:51:09Reef sharks and nurse sharks.
0:51:09 > 0:51:12- Oh.- You OK?
0:51:12 > 0:51:16One big old shark hanging down there, deep.
0:51:17 > 0:51:20Just deep, deep, deep, wouldn't come up.
0:51:20 > 0:51:24May have to reconsider other ways of getting these,
0:51:24 > 0:51:27these little oceanics to, to pose for us.
0:51:27 > 0:51:32With the sharks refusing to appear, the team was forced to resort to
0:51:32 > 0:51:35the tried and tested technique of chumming -
0:51:35 > 0:51:39it was time to give the "little dogs" a bone.
0:51:39 > 0:51:45All we've done is set up a chum line which is a case of hanging an onion bag
0:51:45 > 0:51:49full of the most disgusting offal that you can think of,
0:51:49 > 0:51:52stuff that they couldn't even face putting into Turkey Twizzlers.
0:51:52 > 0:51:57And we're waiting for some sharks to turn up, there's really not much science in it
0:51:57 > 0:52:03apart from making sure that the slick of smell and stuff
0:52:03 > 0:52:06that's gonna attract the sharks goes in the right direction.
0:52:06 > 0:52:10And the right direction for here is, is not over the reef
0:52:10 > 0:52:13but over the blue water where the oceanics live.
0:52:16 > 0:52:21The irresistible smell of rotting fish worked its magic
0:52:21 > 0:52:24and soon the first shark appeared.
0:52:24 > 0:52:27There was no knowing how long it would hang around...
0:52:27 > 0:52:31so the divers needed to get into the water fast.
0:52:35 > 0:52:38The team could at last get to work.
0:52:40 > 0:52:43- To your right!- Right behind you! - Shark!
0:52:44 > 0:52:48The oceanic white tip is a known man-eater,
0:52:48 > 0:52:52a reputation it gained from attacking sailors forced to abandon ship
0:52:52 > 0:52:54during the Second World War.
0:52:57 > 0:53:00Yet this shark seemed almost nervous,
0:53:00 > 0:53:04wary of the two strange objects that had entered its world.
0:53:05 > 0:53:11This was Doug's first chance to get a good look at his "little dog".
0:53:15 > 0:53:16Amazing.
0:53:17 > 0:53:19Totally amazing.
0:53:21 > 0:53:25Goddamn doubting Thomas - think we were out here screwin' around?
0:53:29 > 0:53:32So beautiful, I mean...
0:53:32 > 0:53:38just...real, oceanic wanderers, those big pectorals.
0:53:38 > 0:53:45- Right there, see him?- On the next dive the smell of chum attracted two sharks looking for an easy meal.
0:53:45 > 0:53:48How did Rick feel about getting in with them?
0:53:48 > 0:53:53Is it a smart idea to stick fish guts and chum and when you put a diver in? Hell, no!
0:53:54 > 0:53:56Cos we become part of the chum.
0:53:57 > 0:54:01Diving with known man-eaters is potentially dangerous,
0:54:01 > 0:54:04especially when they arrive expecting food.
0:54:04 > 0:54:09The secret to staying safe is to watch their every move
0:54:09 > 0:54:11and to know when to leave the water.
0:54:17 > 0:54:21These sharks appear relaxed, allowing Rick and Doug to get rare pictures
0:54:21 > 0:54:24of one of the ocean's top predators.
0:54:25 > 0:54:28But white tips are very unpredictable.
0:54:28 > 0:54:32So while the sharks were being nice, the team took full advantage
0:54:32 > 0:54:35to get some of the close-up shots they needed.
0:54:39 > 0:54:42But they were always looking for tell-tale signs
0:54:42 > 0:54:44that things were about to get nasty
0:54:44 > 0:54:47and if in doubt, there was only one option.
0:54:50 > 0:54:52Oh.
0:54:57 > 0:54:59That was exciting.
0:55:03 > 0:55:07The final day saw the arrival of three sharks.
0:55:07 > 0:55:09Wow, he's huge!
0:55:09 > 0:55:10Look at the size of him.
0:55:10 > 0:55:12This is kinda crazy out here now.
0:55:19 > 0:55:23Now, the team began to notice a change.
0:55:23 > 0:55:26The white tips were becoming bolder and more aggressive.
0:55:26 > 0:55:31Their courage seemed to be buoyed by the presence of the other sharks.
0:55:31 > 0:55:35Worse, it was becoming impossible to keep track of three sharks at once
0:55:35 > 0:55:39and soon the white tips began to show more than just curiosity
0:55:39 > 0:55:41towards the divers.
0:55:44 > 0:55:47Some sharks investigate potential prey
0:55:47 > 0:55:50by "bumping" it before they attack.
0:55:55 > 0:55:58Rick recognised the signs.
0:55:58 > 0:55:59It was time to leave.
0:55:59 > 0:56:03He was surrounded and knew the boat had to get to him fast.
0:56:09 > 0:56:11That was too intense.
0:56:11 > 0:56:15The one took, one had my fin it was...
0:56:15 > 0:56:17One had my fin, it would hit me,
0:56:17 > 0:56:21I was filming one, the other would just, "Oh, excuse me."
0:56:23 > 0:56:26It was down to Doug to get the final shots
0:56:26 > 0:56:31and get out before his "nice little dogs" turned really nasty.
0:56:35 > 0:56:36That's enough for me.
0:56:36 > 0:56:40I'm getting out when the getting's good!
0:56:40 > 0:56:44That shark's getting very electric and hot.
0:56:44 > 0:56:50I tell you, he's got a mouth like that, that can take your leg off.
0:56:50 > 0:56:54Fabulous animal but it's into its feeding mode now
0:56:54 > 0:56:57and wants to eat and I don't wanna be part of it.
0:57:00 > 0:57:04For Doug, there was always just one more shot to get.
0:57:07 > 0:57:11But concentrating on what was in front of him meant he couldn't see
0:57:11 > 0:57:13what was creeping up behind.
0:57:19 > 0:57:24And when one of the cruising sharks changed to attack speed...
0:57:27 > 0:57:32it was definitely time to get out and join Rick in the safety of the boat
0:57:32 > 0:57:34before it was too late.
0:57:38 > 0:57:41That was very exciting - it was great.
0:57:41 > 0:57:46They seemed a lot more interested than Rick, I think it's his suit.
0:57:48 > 0:57:50Let's go find a bottle of rum, huh?
0:57:53 > 0:57:56The oceanic white tips had allowed the Planet Earth team
0:57:56 > 0:57:59a rare insight into their world.
0:57:59 > 0:58:04Now it was time to leave these magnificent animals in peace.
0:58:39 > 0:58:41Subtitles by Red Bee Media Ltd
0:58:42 > 0:58:45Email subtitling@bbc.co.uk