0:00:13 > 0:00:15Drop beneath the waves...
0:00:17 > 0:00:19..and you'll discover another world.
0:00:24 > 0:00:25Mysterious.
0:00:29 > 0:00:30Unexplored.
0:00:35 > 0:00:37A world ruled by strange,
0:00:37 > 0:00:39fearsome creatures.
0:00:41 > 0:00:43They're an ancient family
0:00:43 > 0:00:46whose ancestors fought dinosaurs.
0:00:48 > 0:00:51Today, they are every shape,
0:00:51 > 0:00:53every size,
0:00:53 > 0:00:56and hunt in every sea.
0:00:59 > 0:01:02These are the ocean's greatest predators.
0:01:12 > 0:01:16This is the world of the shark.
0:01:37 > 0:01:39Off the coast of Cape Fear
0:01:39 > 0:01:42are the wrecks of over 100 ships.
0:01:45 > 0:01:47A unique place
0:01:47 > 0:01:50where you can get closer than you may like
0:01:50 > 0:01:53to one of the most frightening-looking sharks.
0:02:13 > 0:02:17Ragged tooth sharks gather in these wrecks to feed.
0:02:18 > 0:02:22They show all the characteristics of great ocean hunters.
0:02:23 > 0:02:25A streamlined body,
0:02:25 > 0:02:27and a muscular tail.
0:02:31 > 0:02:33A mouth packed with teeth.
0:02:34 > 0:02:36Teeth that are endlessly replaced.
0:02:41 > 0:02:44A head crammed with sensors to detect their prey.
0:02:48 > 0:02:50Their design is so successful,
0:02:50 > 0:02:54it's barely changed in 400 million years.
0:02:57 > 0:03:00The best place to see these perfect predators in action...
0:03:04 > 0:03:06..is here,
0:03:06 > 0:03:08the tip of South Africa.
0:03:17 > 0:03:21A lone blacktip shark is drawn to a faint sound
0:03:21 > 0:03:23far away in the distance.
0:03:33 > 0:03:36A sound far too faint for human hearing.
0:03:43 > 0:03:44She's not alone for long.
0:03:47 > 0:03:50Other blacktips can hear the sound, too.
0:03:55 > 0:03:59It's the greatest gathering of hunting sharks in the world.
0:04:07 > 0:04:11Hundreds and hundreds of six-foot-long sharks,
0:04:11 > 0:04:13all here because of this.
0:04:16 > 0:04:19Ten million anchovies are swarming up the coast
0:04:19 > 0:04:21on their annual migration.
0:04:23 > 0:04:24Tiny and agile,
0:04:24 > 0:04:27they easily out-manoeuvre a single shark.
0:04:35 > 0:04:37But the blacktips work together.
0:04:41 > 0:04:43Of all the sharks,
0:04:43 > 0:04:46these are the masters of teamwork.
0:04:54 > 0:04:56Some swim underneath the fish,
0:04:56 > 0:04:58trapping them against the surface.
0:04:59 > 0:05:01While others circle the shoal.
0:05:05 > 0:05:07Herding them together.
0:05:11 > 0:05:14And, when the moment is just right...
0:05:15 > 0:05:17..the blacktips attack.
0:05:25 > 0:05:27Striking from every angle,
0:05:27 > 0:05:30the sharks cut off any escape route.
0:05:44 > 0:05:47As the attack builds,
0:05:47 > 0:05:49the fish crush together ever tighter.
0:05:54 > 0:05:56Greedy gannets dive in,
0:05:56 > 0:05:59getting a free meal from the blacktips' hard work.
0:06:26 > 0:06:28The fish huddle at the surface.
0:06:33 > 0:06:35But there's no way out.
0:06:42 > 0:06:46The sea is filled with a snowstorm of fish scales.
0:06:59 > 0:07:04And then these blacktips simply disappear into the blue.
0:07:20 > 0:07:23Sharks belong to one huge extended family.
0:07:26 > 0:07:30And every single family member shares certain key features.
0:07:33 > 0:07:38Their skin is made from thousands of minute teeth coated with enamel.
0:07:42 > 0:07:44Sharks don't have bones.
0:07:44 > 0:07:47Instead, there's a skeleton of rubbery cartilage.
0:07:49 > 0:07:52They all have a row of gill slits,
0:07:52 > 0:07:55usually five along their side.
0:08:00 > 0:08:03There are 510 species of shark.
0:08:04 > 0:08:08The largest is a staggering 40 feet long.
0:08:08 > 0:08:11The smallest could fit in the palm of your hand,
0:08:11 > 0:08:13and it glows in the dark.
0:08:15 > 0:08:18Some have heads shaped like a hammer.
0:08:20 > 0:08:22Others like a chainsaw.
0:08:28 > 0:08:30And there's one with a body so strange...
0:08:33 > 0:08:34..it can hardly be seen at all.
0:08:50 > 0:08:53This master of disguise
0:08:53 > 0:08:56lives in the eastern seas of Indonesia.
0:09:00 > 0:09:02Home to the world's richest coral reef.
0:09:17 > 0:09:22More than 1,500 species of fish swim in these sunlit waters.
0:09:28 > 0:09:31But in the shadows, something is lurking.
0:09:33 > 0:09:36This is the tasselled wobbegong.
0:09:40 > 0:09:43The greatest ambush hunter of all sharks.
0:09:47 > 0:09:50The tassels on his chin look like pieces of coral,
0:09:50 > 0:09:52breaking up his profile.
0:09:55 > 0:09:58His skin is exquisitely camouflaged.
0:10:01 > 0:10:06He lies motionless, staring at the fish.
0:10:10 > 0:10:13His sharp eyes focus on a single spot in front of him...
0:10:15 > 0:10:19..waiting for a victim to stray into range.
0:10:32 > 0:10:34No luck here today.
0:10:36 > 0:10:38Time to try somewhere else.
0:10:47 > 0:10:50The wobbegong is a poor swimmer, but has a routine.
0:10:51 > 0:10:57If one site isn't working, there are other places to set the trap.
0:11:11 > 0:11:16The wobbegong's favourite hideout is the entrance to a cave.
0:11:27 > 0:11:29The fish are wary and keep their distance.
0:11:37 > 0:11:39But the wobbegong has a trick.
0:11:39 > 0:11:43His tail is a lure that attracts his prey.
0:11:45 > 0:11:47Waving it at the back of his cave,
0:11:47 > 0:11:50it mimics a fish already swimming there.
0:11:53 > 0:11:55So, it looks safe to enter.
0:11:59 > 0:12:00Wrong.
0:12:04 > 0:12:07Pressure sensitive cells on the wobbegong's head
0:12:07 > 0:12:10detect the slightest movement.
0:12:26 > 0:12:28As they come ever closer,
0:12:28 > 0:12:31the wobbegong goes onto high alert.
0:12:36 > 0:12:38It's behind you!
0:12:45 > 0:12:47The strike is so fast,
0:12:47 > 0:12:49the other fish never even saw the victim disappear.
0:12:58 > 0:12:59In the blink of an eye...
0:13:05 > 0:13:07..the fish is sucked into the mouth,
0:13:07 > 0:13:12and straight into the stomach to be slowly dissolved and digested.
0:13:36 > 0:13:39Wobbegongs may be the masters of patience...
0:13:40 > 0:13:43..but other members of the shark family
0:13:43 > 0:13:44are in rather more of a hurry.
0:13:50 > 0:13:54The mako is the fastest shark in the world.
0:13:55 > 0:13:57Think torpedo with teeth.
0:14:00 > 0:14:02The tail is packed with muscle.
0:14:04 > 0:14:06The body is sleek and streamlined.
0:14:09 > 0:14:11It has a stabiliser on the side for cornering at speed.
0:14:13 > 0:14:17Like all sharks, the skin is made from minuscule teeth,
0:14:17 > 0:14:20but the mako's is specially textured to minimise drag.
0:14:26 > 0:14:31Here in the open ocean, their dinner, tuna, is quick
0:14:31 > 0:14:34so makos have to be even quicker.
0:14:34 > 0:14:38To see just how fast they are takes a speedboat...
0:14:40 > 0:14:42..towing a camera.
0:14:48 > 0:14:52The shiny housing attracts the attention of all sorts of animals.
0:14:55 > 0:14:57First to follow,
0:14:57 > 0:14:59fur seals.
0:15:03 > 0:15:05Their top speed is 10mph.
0:15:08 > 0:15:10Twice as fast as an Olympic swimmer.
0:15:20 > 0:15:22But there are faster creatures around.
0:15:24 > 0:15:26A pod of common dolphins arrives.
0:15:27 > 0:15:32With super streamlined bodies, their top speed is 20mph.
0:15:40 > 0:15:42But, if the boat accelerates,
0:15:42 > 0:15:44they, too, will drop away.
0:15:55 > 0:15:57Then, at full speed,
0:15:57 > 0:15:59a mako.
0:16:09 > 0:16:12It can sprint at 30mph.
0:16:12 > 0:16:14That's quicker than Usain Bolt.
0:16:16 > 0:16:18Makos have been clocked at 46mph,
0:16:18 > 0:16:21though no-one really knows their limit.
0:16:28 > 0:16:30But it's faster than the speed boat.
0:16:40 > 0:16:43Sharks have adapted to live in every ocean in the world.
0:16:48 > 0:16:51Even here, where the ocean is frozen.
0:16:58 > 0:17:02Under this Arctic ice lives one of the most mysterious sharks of all.
0:17:02 > 0:17:06DOGS WHIMPER AND HOWL
0:17:15 > 0:17:18For centuries, they were known only to the Inuit people.
0:17:29 > 0:17:33They once caught sharks as food for their dogs.
0:17:42 > 0:17:44Today, they use their skills
0:17:44 > 0:17:47to help scientists find and track these sharks.
0:17:53 > 0:17:57Greenland sharks live half a mile down
0:17:57 > 0:17:58in the abyss.
0:18:02 > 0:18:04In this twilight zone,
0:18:04 > 0:18:06there is little to eat,
0:18:06 > 0:18:09and the water is -1.
0:18:09 > 0:18:11Only the salt stops it from freezing.
0:18:20 > 0:18:24A Greenland shark's metabolism is set low to survive the cold.
0:18:28 > 0:18:31He swims at just half a mile an hour,
0:18:31 > 0:18:33but he could live for 200 years.
0:18:39 > 0:18:42In his constant search for food,
0:18:42 > 0:18:45he must emerge from the darkness,
0:18:45 > 0:18:48and slowly, slowly,
0:18:48 > 0:18:50swim to the surface.
0:18:58 > 0:19:01Up in the light, it's a beautiful place.
0:19:10 > 0:19:11But he cannot see it.
0:19:13 > 0:19:14He is blind.
0:19:24 > 0:19:26In these Arctic waters,
0:19:26 > 0:19:31every Greenland shark has a copepod parasite attached to the eyeball.
0:19:32 > 0:19:37This bizarre creature lives only on Greenland sharks,
0:19:37 > 0:19:40gnawing away at the surface of his eye
0:19:40 > 0:19:43until his world drops into shadows.
0:19:55 > 0:19:58He finds his way through the darkness by smell.
0:20:01 > 0:20:04If he picks up the scent of food, he could track it for miles.
0:20:06 > 0:20:09Greenland sharks scavenge anything they can find.
0:20:11 > 0:20:12A dead reindeer,
0:20:12 > 0:20:14even a drowned polar bear.
0:20:25 > 0:20:30Most times, his search for food at the surface finds nothing.
0:20:43 > 0:20:45He drops down again,
0:20:45 > 0:20:47blind and silent...
0:20:48 > 0:20:52..and disappears back into the deep.
0:21:01 > 0:21:04His is a long and lonely life.
0:21:17 > 0:21:20It's not only Greenland sharks that live in the abyss.
0:21:22 > 0:21:25The deep ocean hides other sharks that are even stranger.
0:21:30 > 0:21:34Now, new technology and new cameras mean they can be found.
0:21:38 > 0:21:41A team of Japanese scientists and cameramen
0:21:41 > 0:21:43have spent four years exploring the abyss.
0:21:49 > 0:21:50Over half a mile deep,
0:21:50 > 0:21:53strange creatures appear,
0:21:53 > 0:21:57feeding on the detritus that drifts down from life at the surface.
0:22:17 > 0:22:19Either that,
0:22:19 > 0:22:21or they feed on each other.
0:22:23 > 0:22:25There are predators in the darkness.
0:22:27 > 0:22:31A frilled shark catches prey by lunging forward like a snake,
0:22:31 > 0:22:34snaring victims in its 200 teeth.
0:22:45 > 0:22:47Their mouths open so wide
0:22:47 > 0:22:49they can swallow prey more than half their size.
0:22:55 > 0:22:58Their eyes have built-in image intensifiers
0:22:58 > 0:23:00to detect the faintest glimpse of potential food.
0:23:10 > 0:23:14Some sharks are so well adapted to life in the depths,
0:23:14 > 0:23:16they don't rely on sight at all.
0:23:26 > 0:23:28The goblin shark is a living fossil,
0:23:28 > 0:23:31virtually unchanged for 100 million years.
0:23:39 > 0:23:42The long snout works like a metal detector,
0:23:42 > 0:23:46picking up the minute electro-magnetic field
0:23:46 > 0:23:47given off by fish.
0:23:58 > 0:24:01In the darkness, it drifts towards prey
0:24:01 > 0:24:03until they're directly in front of its jaws.
0:24:21 > 0:24:23The extra reach helps snatch the victim
0:24:23 > 0:24:27and, down here, that can make all the difference.
0:24:38 > 0:24:42Constant darkness and a pressure 100 times greater than at the surface
0:24:42 > 0:24:44makes this a tough place to live.
0:24:46 > 0:24:48But there's one species of shark
0:24:48 > 0:24:51that lives somewhere even more challenging.
0:24:52 > 0:24:55And it's in the most unexpected place.
0:25:05 > 0:25:08The tropical seas of Australia's Great Barrier Reef.
0:25:15 > 0:25:1914 species of shark live in these shallow waters.
0:25:23 > 0:25:27Twice a day, conditions here change drastically.
0:25:31 > 0:25:34And that's what the smallest shark on this reef
0:25:34 > 0:25:35is waiting for.
0:25:43 > 0:25:44Under two feet long,
0:25:44 > 0:25:48an epaulette shark could be eaten by the bigger sharks if it's spotted.
0:25:52 > 0:25:55So, while they're around, it stays well hidden.
0:26:00 > 0:26:03It's waiting for the tide to go out.
0:26:13 > 0:26:17And, on this part of the reef, when the tide turns,
0:26:17 > 0:26:20it's like a plug has been pulled out.
0:26:21 > 0:26:24A billion gallons of water pour away.
0:27:00 > 0:27:03The bigger sharks retreat into deeper water.
0:27:05 > 0:27:09The reef is left as a series of interconnected rock pools.
0:27:15 > 0:27:16Perfect!
0:27:17 > 0:27:20Now the epaulette has the reef all to itself.
0:27:30 > 0:27:34The other rock pool creatures live in fear of this tiny tyrant.
0:27:39 > 0:27:43Its sinuous body is ideal for crawling into crevices.
0:27:45 > 0:27:48Its favourite dish is fresh crab.
0:28:21 > 0:28:23But it's not all going the epaulette's way.
0:28:30 > 0:28:32The tide keeps dropping.
0:28:40 > 0:28:45What was once a pool quickly becomes just a puddle.
0:28:52 > 0:28:56The scorching Australian sun is no place for a shark.
0:28:59 > 0:29:01As the water finally drains away,
0:29:01 > 0:29:04the epaulette is left high and dry.
0:29:19 > 0:29:21No shark can breathe out of water.
0:29:32 > 0:29:35But the epaulette shark has a trick.
0:29:41 > 0:29:44By shutting down its organs one by one
0:29:44 > 0:29:48it can cope without oxygen 60 times longer than a human.
0:29:55 > 0:30:00And if necessary, it switches to survival strategy number two.
0:30:12 > 0:30:17This is the only shark that can walk on land.
0:30:24 > 0:30:26It heads towards the nearest water.
0:30:44 > 0:30:48The fins have become prototype legs.
0:30:57 > 0:31:00At last, the refreshing, cool sea.
0:31:03 > 0:31:06This is a shark that can walk its way out of trouble.
0:31:21 > 0:31:25Epaulettes aren't the only shark whose body shape has evolved
0:31:25 > 0:31:26in surprising ways.
0:31:32 > 0:31:36Thresher sharks have a tail that's the length of their body.
0:31:36 > 0:31:39They use it as a whip, stunning their prey.
0:31:44 > 0:31:47Basking sharks feed on plankton,
0:31:47 > 0:31:49filtering vast quantities of sea water
0:31:49 > 0:31:51through enormous modified gills.
0:31:55 > 0:31:58Nurse sharks have a mouth like a vacuum cleaner.
0:31:58 > 0:32:01Their favourite food is firmly hidden in its shell.
0:32:03 > 0:32:05But one strong suck...
0:32:07 > 0:32:09..and it's out.
0:32:12 > 0:32:15A wide, hammer-shaped head helps this shark
0:32:15 > 0:32:17detect prey hidden in the sand.
0:32:23 > 0:32:25But some sharks have adapted,
0:32:25 > 0:32:27not by changing their bodies...
0:32:29 > 0:32:31..but by changing their behaviour.
0:32:42 > 0:32:47At first sight, whitetip reef sharks don't seem like ferocious predators.
0:33:00 > 0:33:03By day, local fish use their skins as a scratching post.
0:33:09 > 0:33:12Young sea lions have fun harassing them.
0:33:23 > 0:33:26But these sharks are simply biding their time...
0:33:29 > 0:33:32..waiting for the perfect conditions to hunt.
0:33:46 > 0:33:50As darkness falls, the tables begin to turn.
0:33:52 > 0:33:54The whitetips change
0:33:54 > 0:33:56from Dr Jekyll...
0:34:00 > 0:34:02..into Mr Hyde.
0:34:06 > 0:34:09Every available shelter and refuge is taken.
0:34:19 > 0:34:25It's a bad idea to be caught in the open after curfew is called.
0:34:34 > 0:34:36The whitetip pack use their sense of smell
0:34:36 > 0:34:38to home in on the fish.
0:34:40 > 0:34:43Hunting as one, they scour the reef,
0:34:43 > 0:34:46inspecting every nook and crevice.
0:34:48 > 0:34:50You can run,
0:34:50 > 0:34:53or you can hide.
0:34:56 > 0:34:58Either way, the pack will find you.
0:35:03 > 0:35:07Because as they get close, another sense takes over.
0:35:08 > 0:35:09Electricity.
0:35:12 > 0:35:15All living creatures produce a small electrical field.
0:35:20 > 0:35:23Sharks can detect even a few millionths of a volt.
0:35:25 > 0:35:30The electricity from the beating heart of a frightened fish.
0:35:41 > 0:35:45A struggling fish gives off low-frequency sounds
0:35:45 > 0:35:48and that attracts other whitetips,
0:35:48 > 0:35:51their hearing tuned to that particular pitch.
0:35:56 > 0:35:58In the night, the mob rules.
0:36:05 > 0:36:08It's a long wait until dawn.
0:36:17 > 0:36:21At last, the sun starts to rise
0:36:21 > 0:36:25and, like the flick of a switch,
0:36:25 > 0:36:26the attack stops.
0:36:35 > 0:36:38The advantage of darkness over,
0:36:38 > 0:36:40the whitetips head back to rest.
0:36:45 > 0:36:47It's safe for the fish to come out.
0:36:59 > 0:37:02They spend the day lying on the seabed...
0:37:06 > 0:37:07..if they're left in peace.
0:37:18 > 0:37:21But, come the night, the whitetips again will rule the reef.
0:37:31 > 0:37:34Sharks have been the ocean's greatest hunters
0:37:34 > 0:37:37for 400 million years.
0:37:44 > 0:37:46They mastered the seas
0:37:46 > 0:37:48with patience and stealth.
0:37:54 > 0:37:55Astonishing speed.
0:37:58 > 0:38:00Agility and strength.
0:38:04 > 0:38:07There is one shark above all others
0:38:07 > 0:38:11that combines every single one of these skills,
0:38:11 > 0:38:13plus a bit.
0:38:13 > 0:38:18MUSIC: Baby Did A Bad, Bad Thing by Chris Isaak
0:38:19 > 0:38:23The great white shark has it all.
0:38:29 > 0:38:32Speed, strength, stealth.
0:38:34 > 0:38:36And huge teeth.
0:38:39 > 0:38:40It needs them.
0:38:40 > 0:38:44Of all the sharks, it has the hardest prey to catch.
0:38:48 > 0:38:51It hunts on the Cape of Storms,
0:38:51 > 0:38:54Africa's wild south coast.
0:39:01 > 0:39:04It specialises in hunting another predator.
0:39:09 > 0:39:13One that is smart, aggressive and agile.
0:39:20 > 0:39:22One that even eats small sharks.
0:39:25 > 0:39:30Fur seals breed on the islands and feed in the rich waters.
0:39:40 > 0:39:44This female has travelled hundreds of miles to be here...
0:39:47 > 0:39:49..and she's hungry.
0:39:54 > 0:39:56But she has competition.
0:39:57 > 0:40:00Dozens of great whites have arrived,
0:40:00 > 0:40:02all vying for the same food.
0:40:09 > 0:40:11She needs to eat.
0:40:24 > 0:40:26The seals gather in the safety of the kelp.
0:40:46 > 0:40:48The seals need to reach the open ocean to feed.
0:40:51 > 0:40:55To get there, they'll have to run...the gauntlet.
0:41:02 > 0:41:06At first light, these seals gather together
0:41:06 > 0:41:08and make a dash for it.
0:41:17 > 0:41:20But the shark senses their movement
0:41:20 > 0:41:22and she starts to track them.
0:41:26 > 0:41:28Attacking a seal is dangerous.
0:41:28 > 0:41:31Get it wrong and she could lose an eye.
0:41:37 > 0:41:40She stays deep, stalking them.
0:41:42 > 0:41:45If she's to make the kill,
0:41:45 > 0:41:47surprise is everything.
0:41:59 > 0:42:00She misses.
0:42:02 > 0:42:04Now the advantage goes to the seals.
0:42:05 > 0:42:08They scatter, but one has been injured.
0:42:30 > 0:42:32The shark is stronger,
0:42:32 > 0:42:34but the seal is far more agile.
0:43:10 > 0:43:14The seal's strategy is to stay on her tail.
0:43:14 > 0:43:16It's the one place it can't be caught.
0:43:21 > 0:43:25Keep close and then make a sudden dash for it.
0:43:36 > 0:43:39In this murky water, she loses sight of her target.
0:43:43 > 0:43:47But the seal is wounded and she starts to follow the plume of blood.
0:44:18 > 0:44:19It's a clean kill.
0:44:28 > 0:44:33By shaking her head, she rips off chunks she can swallow.
0:44:38 > 0:44:41She drops the seal to get a better grip.
0:44:44 > 0:44:47But the blood is attracting other sharks.
0:44:52 > 0:44:54Her hard-won meal has been taken.
0:44:58 > 0:45:00BIRDS CRY
0:45:05 > 0:45:11Outwitted and outmanoeuvred, she's wasted precious energy.
0:45:17 > 0:45:20Great white sharks burn fuel faster than any other shark.
0:45:23 > 0:45:24She must eat soon.
0:45:39 > 0:45:41Another group of seals heads her way.
0:46:39 > 0:46:42Leaping clear of the water at 20mph...
0:46:45 > 0:46:49..the one-tonne shark catches a seal in mid air.
0:47:12 > 0:47:16It's no wonder that of all the sharks
0:47:16 > 0:47:18The great white is the most famous.
0:47:23 > 0:47:26Sharks are the greatest predators in the ocean.
0:47:33 > 0:47:38And the great white is the greatest predator of them all.
0:48:01 > 0:48:04For two years, the BBC Shark team
0:48:04 > 0:48:07travelled the globe to try and reveal sharks like never before.
0:48:10 > 0:48:12By spending so much time observing them,
0:48:12 > 0:48:15they hoped to show the true nature of sharks.
0:48:20 > 0:48:22And that meant getting closer than ever to the ocean's
0:48:22 > 0:48:24most impressive predators.
0:48:26 > 0:48:28BIKE ENGINES PURR
0:48:33 > 0:48:37Of all the places to find a shark, the Arctic was the most unexpected.
0:48:39 > 0:48:42To film Greenland sharks means diving in sub-zero temperatures
0:48:42 > 0:48:44in uncharted waters.
0:48:44 > 0:48:47WIND HOWLS
0:48:47 > 0:48:50It takes great expertise to cut a hole through ice
0:48:50 > 0:48:52that's eight-feet thick.
0:48:52 > 0:48:54Whenever you come out of the tent
0:48:54 > 0:48:56and you see a hole cut in the ice,
0:48:56 > 0:48:59and no other way out, and you look at it and you think
0:48:59 > 0:49:04"Are we absolutely crazy? How cold is this going to be?"
0:49:06 > 0:49:10Bits of you that are exposed on your face just, you know,
0:49:10 > 0:49:13initially sting and they go numb pretty quickly.
0:49:13 > 0:49:17But mentally, getting in is the hardest part.
0:49:17 > 0:49:19Even with the latest thermal diving suits,
0:49:19 > 0:49:22the crew have just 40 minutes in this freezing water.
0:49:25 > 0:49:28We're just putting hot water in our gloves and our hood.
0:49:28 > 0:49:30You cool down so quickly in there
0:49:30 > 0:49:32that you've really got to go in warm cos, one thing's for sure,
0:49:32 > 0:49:35you're not going to warm up when once you get in.
0:49:44 > 0:49:48On the surface it's -20, but once in the water
0:49:48 > 0:49:50it will feel even colder.
0:49:59 > 0:50:02You go through this tiny little hole into a world
0:50:02 > 0:50:06that is so completely different to what you see above.
0:50:06 > 0:50:08It's like stepping off the planet.
0:50:16 > 0:50:19The ice hole is the only exit to the surface.
0:50:21 > 0:50:24If they lose their way, they'll be trapped.
0:50:30 > 0:50:33There's small pinches and there's small spaces
0:50:33 > 0:50:37so, definitely, in the forefront of your mind
0:50:37 > 0:50:40is where you're going to be able to turn around to come back out.
0:50:40 > 0:50:43So, you definitely take it cautiously and slowly.
0:50:46 > 0:50:48Enduring these freezing temperatures,
0:50:48 > 0:50:50they discover that the Greenland shark
0:50:50 > 0:50:52is perfectly at home in this frozen world.
0:50:57 > 0:51:01It certainly lives in a pretty hostile environment.
0:51:03 > 0:51:07It's bizarre in many ways, and yet, so of its place.
0:51:12 > 0:51:14But the clock is ticking for the crew.
0:51:14 > 0:51:18Their body temperatures are dropping and,
0:51:18 > 0:51:21what's worse, their air supply is beginning to freeze over.
0:51:25 > 0:51:27It's time to get back to the ice hole.
0:51:48 > 0:51:50Don't know if I can talk properly.
0:51:50 > 0:51:53I actually can't because my lips are frozen.
0:51:55 > 0:51:59They have some unique images of the Greenland shark,
0:51:59 > 0:52:03but, to get all the shots they need, the Shark team will endure
0:52:03 > 0:52:05another 13 dives under the ice.
0:52:10 > 0:52:15The team's aim was to film sharks in every ocean habitat -
0:52:15 > 0:52:16even man-made ones.
0:52:21 > 0:52:25It's called the graveyard of the Atlantic.
0:52:25 > 0:52:28Over 100 wrecks off the coast of North Carolina.
0:52:31 > 0:52:33Ragged tooth sharks gather here to feed.
0:52:36 > 0:52:40An opportunity to get eye-to-eye with a fearsome-looking shark.
0:52:45 > 0:52:49- Rachel Butler is in charge of dive safety.- I'm ready.
0:52:49 > 0:52:52- Oxygen analysed?- Yep, O2 analysed.
0:52:52 > 0:52:53Oxygen supply pressure?
0:52:53 > 0:52:56'It's really important that we do these checks because you can't
0:52:56 > 0:52:59'afford for anything to go wrong if you're trapped inside a shipwreck.'
0:53:13 > 0:53:14It's a long way down.
0:53:28 > 0:53:31When you're inside a shipwreck with 50 sharks,
0:53:31 > 0:53:34it does make you think a little bit because they look so fierce -
0:53:34 > 0:53:37especially as they're swimming right over you.
0:53:40 > 0:53:44It turns out the sharks are simply not interested in the film crew.
0:53:51 > 0:53:55The sharks are very misunderstood, very misunderstood.
0:53:55 > 0:53:58They're actually more scared of us than we are of them.
0:53:58 > 0:54:01- They are, they are.- I nearly touched one and it just went - kercheeeww! -
0:54:01 > 0:54:03swam fast away from me. I was thinking,
0:54:03 > 0:54:06"I'm the one that's supposed to be scared of you!"
0:54:10 > 0:54:15But there's one shark where extreme caution is required -
0:54:15 > 0:54:17the great white.
0:54:19 > 0:54:21WAVES CRASH
0:54:23 > 0:54:26To film great white sharks, the team travel
0:54:26 > 0:54:29to their prime hunting ground, the coast of South Africa.
0:54:31 > 0:54:33One of their goals is to film the sharks underwater
0:54:33 > 0:54:35as they prepare to hunt.
0:54:36 > 0:54:39Great whites attack seals at the surface,
0:54:39 > 0:54:42making it the danger zone for any diver -
0:54:42 > 0:54:43so novel precautions are taken.
0:54:45 > 0:54:49I've rigged a rear-view mirror on my camera housing here.
0:54:49 > 0:54:51White sharks are notorious ambush predators,
0:54:51 > 0:54:54so they always seem to come from behind you.
0:54:54 > 0:54:57If the light's blinding and you look into it you can't see anything -
0:54:57 > 0:55:00that's where they're going to come from.
0:55:00 > 0:55:03Andy needs a cage to get to the safety of the seabed.
0:55:13 > 0:55:16You're diving around seal colonies where they're hunting.
0:55:16 > 0:55:17You'd be stupid not be cautious.
0:55:45 > 0:55:49He's able to get a unique perspective from inside the kelp.
0:55:51 > 0:55:54As the shark's attention is focused on the seals,
0:55:54 > 0:55:56it should ignore Andy.
0:56:10 > 0:56:12They're not out to get us.
0:56:12 > 0:56:16They're professional predators that eat seals, fish, dolphins -
0:56:16 > 0:56:18they really don't think much about people
0:56:18 > 0:56:22unless you put yourself in the wrong situation at the wrong time
0:56:22 > 0:56:23and that's your fault.
0:56:29 > 0:56:33In this series, the team got closer to sharks than ever before...
0:56:39 > 0:56:42..but they didn't have a single dangerous shark encounter.
0:56:49 > 0:56:54There's far more to sharks than just being a predator
0:56:54 > 0:56:56and that is what the next programme explores.
0:57:00 > 0:57:03The secret life of the shark family
0:57:03 > 0:57:05involves social networking,
0:57:05 > 0:57:07mysterious gatherings.
0:57:08 > 0:57:12We reveal their secret body language,
0:57:12 > 0:57:13how the young grow up,
0:57:13 > 0:57:16and their complex courtship rituals.