0:00:32 > 0:00:34In all the seas of the world,
0:00:34 > 0:00:41the warm waters of the Tropics contain the richest and most colourful communities.
0:00:47 > 0:00:52Coral reefs. They may seem like underwater paradise,
0:00:52 > 0:00:56but they are perpetual battlegrounds for space.
0:01:00 > 0:01:04Even the corals have to fight for it.
0:01:05 > 0:01:12In this crowded, frenetic community, every individual has to find its own place, its own way of surviving.
0:01:19 > 0:01:24But none of these creatures would be here, if it were not for the coral.
0:01:48 > 0:01:55A coral larva drifts in the open sea, floating in a soup of young reef animals.
0:02:05 > 0:02:12If just one of these coral larvae settles in a suitable spot and survives,
0:02:12 > 0:02:15a new reef will be founded.
0:02:20 > 0:02:26In just a few days, the larva changes form and becomes a polyp, similar to a sea anemone.
0:02:29 > 0:02:33Identical copies bud off, and gradually a colony develops.
0:02:36 > 0:02:43Each polyp surrounds itself with a hard skeleton and from this solid base begins to grow.
0:03:00 > 0:03:05It increases in length by 15 centimetres a year.
0:03:05 > 0:03:10This branching coral is only two years old.
0:03:10 > 0:03:13A mature reef can be thousands.
0:03:24 > 0:03:31Corals provide the foundations on which the entire reef community relies.
0:03:31 > 0:03:36Some organisms, like the Christmas tree worms, live within the coral.
0:03:44 > 0:03:49Others climb out, away from the reef, to filter their food from the water.
0:04:04 > 0:04:09As the community grows, intimate relationships are formed
0:04:09 > 0:04:14and different creatures become dependent on one another.
0:04:16 > 0:04:21Even animals that spend much of their time travelling in the open ocean
0:04:21 > 0:04:24return to the reef for a clean.
0:04:33 > 0:04:38Coral reefs can be home to astounding numbers of fish.
0:04:52 > 0:04:57Here swim the smallest and the largest fish in the sea.
0:05:04 > 0:05:08Whale sharks are only visitors.
0:05:08 > 0:05:14When currents bring nutrient-rich water up from the deep, they come here to feed.
0:05:23 > 0:05:28All these animals are here because of the coral.
0:05:30 > 0:05:35This extraordinary complex maze is built layer upon layer
0:05:35 > 0:05:39by millions and millions of individual animals...
0:05:40 > 0:05:42..polyps.
0:05:54 > 0:05:58Each polyp's flesh is supported by a limestone skeleton.
0:06:04 > 0:06:07Below the gut...
0:06:09 > 0:06:13..is the place where most of the growth occurs.
0:06:13 > 0:06:18Here the living tissue deposits an intricate lattice of limestone.
0:06:22 > 0:06:30Beneath that, the limestone skeleton is bare, having been vacated by the living coral tissues.
0:06:30 > 0:06:35This is the hard structure that forms the foundation of the reef.
0:06:35 > 0:06:39And a single reef can extend for many miles.
0:06:54 > 0:07:02Coral reefs are only found in the clear, warm, shallow waters of the tropics.
0:07:04 > 0:07:07Sunlight is vital to them,
0:07:07 > 0:07:09even though they're animals,
0:07:09 > 0:07:16because inside their flesh live millions of tiny single-celled algae...
0:07:16 > 0:07:18plants.
0:07:18 > 0:07:23And all plants need sunlight to photosynthesise sugars.
0:07:34 > 0:07:3998% of the food that corals consume is produced by the algae.
0:07:42 > 0:07:46Without them, the reef would not exist.
0:07:52 > 0:07:58Like any other plant, algae need just the right amount of light,
0:07:58 > 0:08:00not too much, not too little.
0:08:04 > 0:08:07The corals regulate that
0:08:07 > 0:08:13with pigments that we can only see when they are illuminated by ultraviolet light.
0:08:50 > 0:08:57Most corals, for protection, spend the day withdrawn into their stoney fortresses.
0:08:57 > 0:09:02Even then, they're not safe from the jaws of these butterfly fish.
0:09:19 > 0:09:26At night, the corals take in water, expand their tentacles, and emerge to feed.
0:09:43 > 0:09:46They collect plankton.
0:09:47 > 0:09:53Each tentacle has batteries of stinging cells which fire on contact.
0:09:53 > 0:09:57Once the prey is caught, it's passed down to the polyp's mouth.
0:10:07 > 0:10:14It's at night when the polyps are extended that they add to the limestone foundations beneath them.
0:10:23 > 0:10:30Inevitably, the corals begin to overgrow each other and that means trouble.
0:10:37 > 0:10:43When neighbours get too close, they detect one another's presence chemically.
0:10:43 > 0:10:48The aggressor, on the right, prepares for battle.
0:10:57 > 0:10:59The polyps extrude their guts...
0:10:59 > 0:11:03and simply digest their rivals alive.
0:11:26 > 0:11:33A no-man's land, a band of white skeleton, is the only evidence of the night's border dispute.
0:11:41 > 0:11:45Some corals are targeted by yet more deadly predators.
0:11:54 > 0:11:59Predators that can crawl in search of their victims.
0:12:01 > 0:12:07Crown of thorns starfish - poisonous, invincible eating machines.
0:12:07 > 0:12:11They also extrude their gut and digest coral wholesale.
0:12:28 > 0:12:31But some corals have help.
0:12:31 > 0:12:39Small crabs living within their branches resist these onslaughts and defend their home.
0:12:48 > 0:12:53They launch an attach on the vulnerable underside of the starfish.
0:13:11 > 0:13:18Even the crown of thorns will retreat from such a determined attack and this coral is left unharmed.
0:13:27 > 0:13:32Hump-head parrot-fish, nearly a metre and a half in length.
0:13:32 > 0:13:37Their jaws are so powerful they can bite through rock.
0:13:41 > 0:13:46When they descend to feed, the reef itself is under threat.
0:13:57 > 0:14:04They are indiscriminate feeders, taking both rock and coral alike in their quest for algae.
0:14:16 > 0:14:20These fish play a large part in the erosion of the reef.
0:14:20 > 0:14:25The rock and coral they swallow emerges later as a fine sand.
0:14:25 > 0:14:30On a single reef, they can produce tonnes of it every year.
0:14:43 > 0:14:49This soft sand forms the tropical beaches that we find so alluring.
0:15:01 > 0:15:08Over time, the sand builds up to form an island, which is then colonised by animals and plants.
0:15:17 > 0:15:19Trees take root.
0:15:19 > 0:15:22Birds arrive.
0:15:26 > 0:15:31The guano from thousands of terns which have chosen to nest here
0:15:31 > 0:15:36enriches the sandy soil, which then can support more plants.
0:15:38 > 0:15:45But these terns, like other sea birds, depend on the ocean for their food.
0:15:54 > 0:16:00Below water on the reef, there is not only competition for living space,
0:16:00 > 0:16:04but a continual contest between predators and prey.
0:16:11 > 0:16:16It's the arms race between them that, over millions of years,
0:16:16 > 0:16:20has produced today's extraordinary diversity of form.
0:16:30 > 0:16:34Jacks are one of the key predators on the reef.
0:16:34 > 0:16:37Their weapon is speed.
0:16:50 > 0:16:57They seek silversides and THEIR defence is to congregate in confusing shoals of shimmering silver.
0:17:02 > 0:17:07The jacks deal with that by herding the silversides onto the reef.
0:17:13 > 0:17:20Here the jacks have a better chance of separating individual fish from the shoal.
0:17:33 > 0:17:38The jacks can now catch the isolated individuals with lightning attacks.
0:17:52 > 0:17:59It's far safer to be hidden on the reef itself, within the tunnels of a sponge, for example.
0:17:59 > 0:18:03These tiny shrimp are no bigger than grains of rice.
0:18:08 > 0:18:11These shrimps are unique.
0:18:11 > 0:18:18It's recently been discovered that they have a sophisticated social system, similar to that of bees.
0:18:18 > 0:18:26All members of the colony are the offspring of one female - the queen, who is the only one to produce eggs.
0:18:34 > 0:18:41As in a colony of bees, different individuals are specialised for particular tasks.
0:18:41 > 0:18:47Some are guards and are armed with especially large and powerful claws.
0:18:51 > 0:18:56They are on watch at all times, ready to tackle intruders.
0:19:07 > 0:19:13A polychaete worm. For it, a sponge is an excellent hunting ground.
0:19:29 > 0:19:35In such a maze of tunnels, attack can come at any time from any quarter.
0:20:04 > 0:20:09Once the guards are alerted, the worm loses its advantage.
0:20:15 > 0:20:19Better to retreat intact than risk serious injury.
0:20:23 > 0:20:28The sponge makes a safe home for the shrimps and supplies them with food,
0:20:28 > 0:20:32so that they never need venture outside.
0:20:32 > 0:20:39An establishment that provides for all their needs is clearly well worth defending.
0:20:41 > 0:20:47Just as shrimps guard their home, other animals defend their hunting grounds.
0:20:50 > 0:20:55Glass fish make tempting prey for the red-mouthed grouper.
0:20:55 > 0:21:02Its strategy is to swim slowly amongst them until they no longer see it as a threat.
0:21:13 > 0:21:16There are other fish here too.
0:21:16 > 0:21:23Lion fish are ambush predators, taking their time and watching for the right moment.
0:21:26 > 0:21:30But there isn't room here for two predators.
0:21:36 > 0:21:43The grouper, braving the lion fish's poisonous spines, tries to evict its rival.
0:21:59 > 0:22:01But lion fish are persistent.
0:22:01 > 0:22:06This grouper spent many hours simply defending his hunting patch.
0:22:23 > 0:22:27Some animals prefer to avoid conflict whenever possible.
0:22:27 > 0:22:32These harlequin shrimp, having captured the starfish,
0:22:32 > 0:22:38are taking it back to a safe house beyond the reach of competitors and danger.
0:22:38 > 0:22:45The problem with starfish is that they have minds of their own and five large, sticky arms.
0:22:46 > 0:22:53By the time the shrimps have prised off one arm, another has reattached itself.
0:23:04 > 0:23:11Only by manoeuvring the starfish on to its back, can they have any hope of gaining the advantage.
0:23:20 > 0:23:23Even so, getting it back home
0:23:23 > 0:23:26is a major undertaking.
0:23:36 > 0:23:38The starfish is now a living larder.
0:23:38 > 0:23:44If the shrimps can hang on to it, it will feed them for days to come.
0:23:44 > 0:23:51The top of the reef is usually covered by a thin layer of green algae,
0:23:51 > 0:23:55another living larder, and many fish depend on it.
0:24:01 > 0:24:06Powder blue tangs defend their right to graze on a particular patch.
0:24:06 > 0:24:12But for a larder as well-stocked as this, there is always competition.
0:24:34 > 0:24:39When a shoal of convict tangs decide to graze, little can stop them.
0:24:50 > 0:24:54Powder blue tangs try to keep them off.
0:25:03 > 0:25:07But they are overwhelmed by sheer numbers.
0:25:12 > 0:25:16The territory is stripped of algae in minutes.
0:25:31 > 0:25:35The blue tangs appear to be fighting a losing battle.
0:25:40 > 0:25:44But, eventually, they begin to get the upper hand.
0:25:57 > 0:26:04They persist with their attacks until the marauders are well on their way.
0:26:18 > 0:26:24When night falls, some very strange creatures creep out of crevices
0:26:24 > 0:26:27and crawl over the reef.
0:26:38 > 0:26:40This moving bush is an animal,
0:26:40 > 0:26:46a basket star, which spreads out its arms to catch the night's plankton.
0:27:08 > 0:27:10The reef becomes uncannily tranquil.
0:27:13 > 0:27:17The fish retire, hiding themselves where they can.
0:28:14 > 0:28:19The marbled rays come out to hunt for prey buried in the sand...
0:28:21 > 0:28:25..using electroreceptors to scan the sea bed.
0:28:30 > 0:28:33Their activity attracts sharks.
0:28:51 > 0:28:54White tips.
0:29:18 > 0:29:23At night, when vision is of little use, sharks have a real advantage.
0:29:24 > 0:29:29They can still use both smell and electroreception to track fish.
0:29:38 > 0:29:43These sharks are also hunting for fish concealed within the reef.
0:29:49 > 0:29:56Their slender shape enables them to squeeze through surprisingly narrow gaps.
0:30:07 > 0:30:10There is nowhere to hide.
0:30:27 > 0:30:32Few animals are safe during these feeding frenzies.
0:31:22 > 0:31:28Night after night, the reef animals are subjected to these raids.
0:31:45 > 0:31:49But life on the reef is not just about food.
0:31:49 > 0:31:51It's also about sex.
0:31:53 > 0:31:57There are many different breeding strategies,
0:31:57 > 0:32:03but each is aimed at maximising the number of young that will survive.
0:32:05 > 0:32:12Every afternoon for two months, brown surgeonfish can be seen streaming across reefs
0:32:12 > 0:32:15in the Red Sea.
0:32:15 > 0:32:21They all head for the same place, usually some prominent feature.
0:32:26 > 0:32:29Here they wait for the light to fade.
0:32:31 > 0:32:38Suddenly females within the group make a dash away from the reef to release their eggs.
0:32:38 > 0:32:43They're immediately followed by the quickest and closest of the males,
0:32:43 > 0:32:48all of whom are striving to fertilise the eggs.
0:32:59 > 0:33:04Inevitably others come here to feast on such easy food.
0:33:09 > 0:33:16As the surgeonfish spawn, fusiliers move in above to eat the nutritious eggs.
0:33:34 > 0:33:41These are just the first of many predators which will feed on the eggs and developing larvae
0:33:41 > 0:33:45as they drift in the ocean during the next few weeks.
0:33:45 > 0:33:49Other fish are less casual about their eggs.
0:33:55 > 0:34:00Banded pipe fish stay close to a small chosen area on the reef.
0:34:00 > 0:34:07Every morning at sunrise, the female leaves her sleeping site and swims to find her partner.
0:34:11 > 0:34:15For ten minutes or so, they remain together,
0:34:15 > 0:34:20reaffirming the bond that is essential to their partnership.
0:34:26 > 0:34:31They swim together around his territory in a simple greeting dance.
0:34:33 > 0:34:38Throughout the summer, when the female's eggs are ripe,
0:34:38 > 0:34:42courtship begins in earnest in the early morning.
0:34:42 > 0:34:49It takes time, and after about two hours, they rise together off the sea bed, entwining their bodies.
0:34:54 > 0:34:58The male rubs himself against the female
0:34:58 > 0:35:00stimulating her to release her eggs.
0:35:06 > 0:35:10And now, swiftly, the male takes them.
0:35:16 > 0:35:22The eggs, now stuck to his belly, are patted down to ensure that they stay there.
0:35:43 > 0:35:50The female then leaves him, but every morning she will return for a session of synchronised swimming,
0:35:50 > 0:35:54and so ensure that their bond is maintained.
0:35:55 > 0:35:58Ten days later,
0:35:58 > 0:36:03under cover of darkness, the male shakes his body,
0:36:03 > 0:36:05and the young pipe fish are born.
0:36:12 > 0:36:16Only now are they independent of their parents.
0:36:16 > 0:36:21Since the male takes charge of the eggs when they're laid,
0:36:21 > 0:36:25the female can start immediately producing the next batch.
0:36:25 > 0:36:31Without his help, they'd only breed every 20 days, rather than every 10.
0:36:31 > 0:36:38So, by sharing the work, they're doubling the number of young they can produce in any one year.
0:36:47 > 0:36:50The flamboyant cuttlefish.
0:36:54 > 0:37:01Unlike most cuttlefish, this one spends much of its time walking, not jetting, across the sea bed.
0:37:01 > 0:37:04This is a male.
0:37:09 > 0:37:14He is using his colourful display to try and seduce the larger female,
0:37:14 > 0:37:17who seems unimpressed.
0:37:28 > 0:37:30Eventually, she concedes.
0:37:34 > 0:37:39The final event, the transfer of sperm, is very quick.
0:37:45 > 0:37:47TRUMPETING
0:38:00 > 0:38:02A singing, male, humpback whale.
0:38:12 > 0:38:16Humpbacks are only visitors to the reef.
0:38:16 > 0:38:24After a pregnancy that lasted a year, the females come here to give birth and suckle their newly-born young.
0:38:24 > 0:38:28Their investment in their single offspring is considerable,
0:38:28 > 0:38:33for each female will continue to nurse it for a further 6-12 months.
0:38:34 > 0:38:37The males are here to mate.
0:38:46 > 0:38:51The lone males sing to establish their relative seniority.
0:38:55 > 0:39:01The louder and longer the song, the bigger and stronger the singer.
0:39:32 > 0:39:39The better the song, the larger the male, the more mating opportunities he will get.
0:39:43 > 0:39:47All these different mating strategies have the same aim -
0:39:47 > 0:39:54to ensure that the greatest number of offspring will live long enough to breed themselves.
0:40:00 > 0:40:03Corals also reproduce sexually,
0:40:03 > 0:40:08but being fixed to the sea bed, they can't move to find a mate.
0:40:08 > 0:40:12Somehow they must synchronise their sexual activity
0:40:12 > 0:40:19and they do so using the rise in water temperatures of spring and the phases of the moon.
0:40:29 > 0:40:36A few days after the full moon, in late spring, when tidal currents are at their weakest,
0:40:36 > 0:40:41the corals of the Great Barrier Reef are ready to spawn.
0:40:48 > 0:40:53Some corals are male and release clouds of sperm.
0:40:53 > 0:40:57Nearby, a female will be releasing eggs.
0:41:13 > 0:41:18Other species of coral are both male and female.
0:41:22 > 0:41:25These release packages of eggs
0:41:25 > 0:41:28already prewrapped in sperm.
0:42:19 > 0:42:26Bundles of eggs and sperm float to the surface to mix with others from further along the reef.
0:42:32 > 0:42:37Each kind of coral times its release to a certain hour on a certain night.
0:42:37 > 0:42:41That maximises the chances of cross-fertilisation.
0:42:48 > 0:42:53The fertilised eggs drift away from the reef.
0:43:22 > 0:43:27The stormy season brings real danger to the animals of the reef.
0:43:33 > 0:43:38Lobsters in the Caribbean sense a change in the water.
0:43:39 > 0:43:44The temperature drops and powerful ocean swells disturb the sand.
0:43:46 > 0:43:48Under the cover of darkness,
0:43:48 > 0:43:55they emerge to run before the storm and risk crossing the exposed sand flats
0:43:55 > 0:43:58to seek shelter in deeper water.
0:44:03 > 0:44:06Every year, they make this journey.
0:44:13 > 0:44:18From all over the reef, lobsters come to join the march.
0:44:18 > 0:44:23They conserve energy by travelling in one another's slipstream.
0:44:30 > 0:44:35And there is the added benefit of safety in numbers.
0:44:48 > 0:44:53By daybreak, they've reached the edge of the deep reef and down they go.
0:44:53 > 0:45:01For the rest of the stormy season, they will remain in the shelter of deep water, out of harm's way.
0:45:17 > 0:45:22Sometimes during the stormy season, a hurricane builds.
0:45:22 > 0:45:27And then the very structure of the reef itself is under threat.
0:46:54 > 0:46:59An entire reef can be destroyed by just one big storm.
0:47:00 > 0:47:04Hundreds of years of growth gone in a few hours.
0:47:21 > 0:47:26Out in the ocean, new life continues to develop.
0:47:26 > 0:47:30In time, coral larvae will return to colonise the rubble
0:47:30 > 0:47:35and a new reef will grow on the wasteland.
0:47:52 > 0:47:59To get pictures of sharks requires some care and a good understanding of shark behaviour.
0:47:59 > 0:48:06The Blue Planet team has encountered many of the world's 400 kinds of shark
0:48:06 > 0:48:11and by treating them with caution and respect no-one was attacked.
0:48:11 > 0:48:18One of the richest areas for sharks is in the Pacific waters of the Central Americas -
0:48:18 > 0:48:20the "Island Of The Sharks".
0:48:20 > 0:48:22Our teams filmed both day and night.
0:48:32 > 0:48:39Cameramen Bob Cranston and Peter Scoones have had a lot of experience with sharks,
0:48:39 > 0:48:43and Bob has worked in these waters before.
0:48:43 > 0:48:49They hope to film the feeding behaviour of white tip sharks -
0:48:49 > 0:48:53a medium-sized species which hunts in packs.
0:48:53 > 0:49:00For filming at night, especially sharks in a big area, we needed quite a bit of light.
0:49:00 > 0:49:03Little battery lights wouldn't do.
0:49:03 > 0:49:06We brought in a generator
0:49:06 > 0:49:11and cables coming down to 650 Watt lights.
0:49:18 > 0:49:23I don't think the sharks were disturbed at all by the light.
0:49:23 > 0:49:28These sharks are clued in to little electronic impulses from each other
0:49:28 > 0:49:31and also from the prey.
0:50:06 > 0:50:14To reach this remote location our dive boat had sailed 300 miles off the west coat of Costa Rica
0:50:14 > 0:50:16to the tiny isolated island of Cocos.
0:50:16 > 0:50:19Although it's only six miles long,
0:50:19 > 0:50:24it attracts an enormous concentration of marine life.
0:50:27 > 0:50:29This is a big event.
0:50:29 > 0:50:31This is a place in this vast ocean.
0:50:31 > 0:50:37And the deep water currents come in and hit this island,
0:50:37 > 0:50:39sea mount, whatever you want to call it.
0:50:39 > 0:50:42It upwells,
0:50:42 > 0:50:44brings up nutrients for little fish.
0:50:44 > 0:50:49The bigger fish feed on the little fish and the sharks feed on them.
0:50:49 > 0:50:52The whole food chain is right here.
0:50:52 > 0:50:53We're here to film it.
0:50:53 > 0:50:57With so many different subjects to choose from
0:50:57 > 0:51:00the team made up to four dives a day
0:51:00 > 0:51:04and some of the encounters were quite unexpected.
0:51:23 > 0:51:26Some sharks keep swimming to breathe
0:51:26 > 0:51:31but the white tip reef shark can sit on the bottom
0:51:31 > 0:51:36and pump water across its gills by moving its mouth up and down.
0:51:46 > 0:51:51One morning we woke up and there was this big ship,
0:51:51 > 0:51:53a helicopter on its back deck.
0:51:53 > 0:51:57We negotiated to get some flight time
0:51:57 > 0:52:00and shoot some aerials of Cocos.
0:52:00 > 0:52:05Wonderful, because few have seen Cocos from the air.
0:52:16 > 0:52:20In Cocos's micro-climate it rains almost every day.
0:52:20 > 0:52:25The water has been churning up the sediment near the shore,
0:52:25 > 0:52:29making water visibility unacceptable.
0:52:29 > 0:52:31It was time to move on.
0:52:31 > 0:52:34This is our last evening at Cocos.
0:52:34 > 0:52:36We've had two sunny days out of 18.
0:52:36 > 0:52:41Tomorrow we're gonna take a day off and cruise to Malpelo
0:52:41 > 0:52:45which is a little spot out in this huge ocean.
0:52:45 > 0:52:47It'll be an easy day.
0:52:47 > 0:52:52I need one. It's been 20 days of diving every day.
0:52:52 > 0:52:54I'm worn out.
0:52:54 > 0:53:00Malpelo is a barren volcanic rock 300 miles south of Cocos.
0:53:00 > 0:53:06Bob spent the 36-hour journey doing essential maintenance to his diving equipment.
0:53:07 > 0:53:13The tiny island of Malpelo is inhabited - and not just by seabirds.
0:53:13 > 0:53:15To extend their fishing rights,
0:53:15 > 0:53:20Columbia has placed a permanent garrison on the island.
0:53:20 > 0:53:25The welcome distraction of visitors must have been a relief.
0:53:27 > 0:53:31This precarious rope ladder is the only way onto the island.
0:53:31 > 0:53:35Volcanic cliffs rise straight out of the sea,
0:53:35 > 0:53:37making the shores treacherous.
0:53:37 > 0:53:41Once ashore it's an arduous climb in the extreme heat.
0:53:41 > 0:53:46Those guys who climbed Mount Everest,
0:53:46 > 0:53:50they had sherpas to carry their gear up the mountain.
0:53:50 > 0:53:52It was nice and cool.
0:53:52 > 0:53:59The producer picked the hottest day of the year to climb this rock.
0:53:59 > 0:54:04The volanic rocks of Malpelo soar almost vertically out of the sea bed.
0:54:04 > 0:54:07Deep ocean currents run up against the island
0:54:07 > 0:54:10and rise to the surface,
0:54:10 > 0:54:12carrying a soup of nutrients.
0:54:12 > 0:54:18The result is an oasis of life in a desert of open ocean.
0:54:27 > 0:54:32The fertility of Malpelo attracts an enormous number of predators.
0:54:32 > 0:54:37One of the most impressive spectacles is called a bait-ball.
0:54:39 > 0:54:44A shoal of small fist are corralled into a ball near the surface
0:54:44 > 0:54:47and then attacked by predators such as tuna.
0:54:47 > 0:54:51But bait-balls are unpredictable, and may only last
0:54:51 > 0:54:57a few minutes. Our team were extremely lucky to film this one.
0:54:59 > 0:55:01That wasn't a very big bait-ball.
0:55:01 > 0:55:06Probably only 400-500 fish, about this big around.
0:55:06 > 0:55:10As soon as I jumped in the water, I could hear a roar.
0:55:12 > 0:55:18This sound of scales flying... Bap, bap, bap, bap, bap!
0:55:18 > 0:55:22Yellowfin tuna - wham! Wham! Wham! Silky sharks - smash! Smash!
0:55:22 > 0:55:26And then, in about three minutes,
0:55:26 > 0:55:30it's all over. They ate them all.
0:55:30 > 0:55:35Malpelo was still to hold one more surprise for our crew,
0:55:35 > 0:55:40only discovered when they dived on the other side of the island.
0:55:40 > 0:55:45They'd seen the oceanic silky sharks before, but not in such numbers.
0:55:49 > 0:55:54The silky sharks are a beautiful shark.
0:55:54 > 0:55:59What makes them so fascinating is that there's thousands of them.
0:56:02 > 0:56:07I don't think you have anything to be worried about or frightened of
0:56:07 > 0:56:09if there's no bait in the water.
0:56:09 > 0:56:13If you were to introduce something for them to feed on,
0:56:13 > 0:56:16then they start competing with one another,
0:56:16 > 0:56:21and then you might smell like a fish, and you could get bit.
0:56:21 > 0:56:27But under normal conditions they're a very curious shark.
0:56:27 > 0:56:31They come up to you, which makes it good for photography.
0:56:31 > 0:56:34They bump and push off your camera.
0:56:34 > 0:56:39I think they want to find out what you are and what you're doing here.
0:56:39 > 0:56:42It's a very unique place.
0:56:43 > 0:56:46You're diving on the edge of reality.
0:57:31 > 0:57:37Next week, Blue Planet enters a world governed by the moon -
0:57:38 > 0:57:41a world dominated by tides,
0:57:41 > 0:57:47that spell life and death in the ocean.