0:00:26 > 0:00:29WIND HOWLS
0:00:32 > 0:00:34ICE CREAKS AND GROANS
0:00:34 > 0:00:37In the far north,
0:00:37 > 0:00:40after three dark months of winter...
0:00:46 > 0:00:48..a world is waiting...
0:00:51 > 0:00:53..for a trigger.
0:00:56 > 0:00:58The sunshine of spring.
0:01:10 > 0:01:13Starfish are the first to respond.
0:01:25 > 0:01:28They race for the highest point...
0:01:30 > 0:01:33..and sensing changes in the water,
0:01:33 > 0:01:35with the tips of their tube feet...
0:01:38 > 0:01:39..they spawn.
0:01:54 > 0:01:57Sea cucumbers,
0:01:57 > 0:01:59with only their mouths exposed,
0:01:59 > 0:02:01now emerge.
0:02:11 > 0:02:14They collect as many starfish eggs as they can.
0:02:28 > 0:02:33Which is quite a lot, when you've got ten arms.
0:02:44 > 0:02:47Now sea pens rise up to claim a share.
0:02:58 > 0:03:02The creatures here must grab what they can of this annual banquet.
0:03:07 > 0:03:12For the light has also set in motion the greatest transformation of all.
0:03:16 > 0:03:19Fronds of kelp, a marine alga,
0:03:19 > 0:03:21rise towards the surface,
0:03:21 > 0:03:24lifted by their gas-filled bladders.
0:03:36 > 0:03:39Soon, a marine forest has materialised...
0:03:44 > 0:03:47..teeming with life of all kinds.
0:03:52 > 0:03:56These green seas are some of the most productive,
0:03:56 > 0:03:59but fiercely competitive, waters
0:03:59 > 0:04:00in all the oceans.
0:04:18 > 0:04:20The southern tip of Africa.
0:04:23 > 0:04:26Here, two great oceans collide.
0:04:30 > 0:04:34SEA ROARS
0:04:37 > 0:04:42In the shallows, fed by rich currents,
0:04:42 > 0:04:45are bountiful forests of kelp.
0:04:58 > 0:05:01Barely visible except for the pulsating siphon
0:05:01 > 0:05:05through which it breathes, a common octopus,
0:05:05 > 0:05:07waiting for prey to pass by.
0:05:12 > 0:05:15A crab will do.
0:05:21 > 0:05:24The octopus sets off in pursuit.
0:05:56 > 0:05:57And then lurks...
0:05:59 > 0:06:02..with the patience of an ambush hunter.
0:06:27 > 0:06:30But the octopus shares the Cape waters
0:06:30 > 0:06:33with a great concentration of other predators.
0:06:40 > 0:06:43Fur seals...
0:06:44 > 0:06:46..and sharks.
0:06:49 > 0:06:51They all eat octopus...
0:06:53 > 0:06:55..if they can find one.
0:07:03 > 0:07:06And pyjama sharks are experts...
0:07:08 > 0:07:10..at hunting in the undergrowth.
0:07:18 > 0:07:20Time to disappear.
0:07:27 > 0:07:30But these tough-skinned little sharks
0:07:30 > 0:07:33are small enough to reach deep into crevices.
0:07:52 > 0:07:56But the octopus is far from finished.
0:07:58 > 0:08:02She slips her tentacles into the shark's gills.
0:08:03 > 0:08:06That prevents the shark from breathing.
0:08:10 > 0:08:13So, the shark has to let go.
0:08:24 > 0:08:27When caught out in the open, and vulnerable,
0:08:27 > 0:08:31this octopus does something truly extraordinary...
0:08:33 > 0:08:35..and never recorded before.
0:08:46 > 0:08:48She disguises herself...
0:08:50 > 0:08:53..with a protective armour of shells.
0:08:58 > 0:09:02She's hiding...in plain sight.
0:09:13 > 0:09:16The shark can sense its prey...
0:09:29 > 0:09:31..but the shells confuse it.
0:09:38 > 0:09:40In a forest full of hungry mouths,
0:09:40 > 0:09:45superior wits allow this octopus to stay alive.
0:09:56 > 0:10:02Forests of kelp flourish in seasonal waters around the globe...
0:10:06 > 0:10:09..particularly along the Pacific Coast of North America.
0:10:18 > 0:10:21Here, the biggest kelps of all
0:10:21 > 0:10:23grow in vast forests,
0:10:23 > 0:10:26stretching for hundreds of miles.
0:10:31 > 0:10:34In some places, the giant fronds
0:10:34 > 0:10:37rise up to 60 metres tall.
0:10:43 > 0:10:47The thickets they create are crowded with life.
0:10:55 > 0:11:00Competition here, for space and food, is intense.
0:11:13 > 0:11:17A challenging problem for the Garibaldi fish.
0:11:24 > 0:11:27He tends to his patch of seaweed,
0:11:27 > 0:11:30filled with tiny creatures that he eats.
0:11:38 > 0:11:43As with most farmers, his work never ends.
0:11:48 > 0:11:51He removes snails and any other grazers
0:11:51 > 0:11:53that come to eat his algae...
0:12:12 > 0:12:14..no matter how big they are.
0:12:24 > 0:12:28He has to deal with pests of all kinds.
0:12:31 > 0:12:33This can be the worst of them -
0:12:33 > 0:12:38sea urchins that can scrape off every vestige of algae from a rock.
0:12:39 > 0:12:41Its spines are needle-sharp.
0:12:45 > 0:12:47Somehow, the Garibaldi must remove it.
0:13:01 > 0:13:04But the problem with sea urchins...
0:13:09 > 0:13:12..is that they just keep coming.
0:13:27 > 0:13:32When evening arrives and the light fades, he has to stop.
0:13:32 > 0:13:35He not only needs a rest, he needs to hide.
0:13:40 > 0:13:44Because at night, predators prowl through these forests.
0:13:49 > 0:13:51A torpedo ray,
0:13:51 > 0:13:55capable of stunning its victim with 45 volts of electricity.
0:14:07 > 0:14:09While the Garibaldi hides...
0:14:11 > 0:14:14..the urchins can feed without interruption.
0:14:23 > 0:14:26The light returns...
0:14:29 > 0:14:33..and he finds his farm is once again under attack.
0:14:50 > 0:14:52Urchins, like locusts,
0:14:52 > 0:14:55have the ability to swarm.
0:15:01 > 0:15:05And this can be disastrous, not just for the Garibaldi,
0:15:05 > 0:15:09but for the kelp forest itself.
0:15:21 > 0:15:24All the vegetation is now under attack.
0:15:53 > 0:15:56The urchins move through the forest,
0:15:56 > 0:15:59cutting through the kelp fronds
0:15:59 > 0:16:01and leaving behind vast barrens.
0:16:05 > 0:16:09These urchin armies have felled many kelp forests
0:16:09 > 0:16:12along the Pacific Coast of North America.
0:16:19 > 0:16:21But help is at hand.
0:16:41 > 0:16:43Sea otters.
0:16:47 > 0:16:52All other kinds of otters spend much of their lives on land,
0:16:52 > 0:16:55but sea otters rarely leave the water.
0:16:59 > 0:17:03At first, a newly-born pup is not a very good swimmer,
0:17:03 > 0:17:08so its mother spends hours grooming its fur to make it buoyant.
0:17:15 > 0:17:19But to provide her youngster with milk and keep herself warm,
0:17:19 > 0:17:23she must eat up to 30% of her body weight every day.
0:17:42 > 0:17:46She does that by eating shellfish.
0:17:51 > 0:17:55And urchins are among a sea otter's favourite delicacies.
0:18:14 > 0:18:19In the past, sea otters were hunted so intensively for their fur
0:18:19 > 0:18:21that they came close to extinction.
0:18:26 > 0:18:32With them gone, many kelp forests were replaced with urchin barrens.
0:18:42 > 0:18:44Today, sea otters are protected...
0:18:48 > 0:18:51..and as their numbers slowly return,
0:18:51 > 0:18:54many of the kelp forests are recovering, too.
0:19:10 > 0:19:12Now, in some remote places,
0:19:12 > 0:19:14sea otters are so numerous
0:19:14 > 0:19:18they assemble in huge rafts...
0:19:22 > 0:19:26..something that hasn't been seen for over a century.
0:20:08 > 0:20:11In the sun-drenched shallows off Australia...
0:20:12 > 0:20:18..kelp is replaced by the sea's only flowering plants,
0:20:18 > 0:20:20sea grass.
0:20:28 > 0:20:31The most extensive of these marine grasslands
0:20:31 > 0:20:35can stretch for over 3,000 square miles.
0:20:49 > 0:20:53All across the tropics, they're patrolled by tiger sharks.
0:20:57 > 0:21:00They can grow up to five metres in length...
0:21:07 > 0:21:09..and have powerful crushing jaws.
0:21:18 > 0:21:21Green turtles are their prey.
0:21:26 > 0:21:30The turtles feed almost entirely on sea grass.
0:21:32 > 0:21:36A single one can consume up to two kilos of it in a day.
0:21:53 > 0:21:55But they can never rest easy.
0:22:06 > 0:22:10Healthy turtles will keep well away from an approaching shark.
0:22:25 > 0:22:28And just by keeping the turtles on the move,
0:22:28 > 0:22:33the sharks prevent any one patch of sea grass from being overgrazed.
0:22:39 > 0:22:42And that has benefits for us all.
0:22:50 > 0:22:54A patch of sea grass can absorb and store
0:22:54 > 0:22:5735 times as much carbon dioxide
0:22:57 > 0:23:01as the same area of a rainforest.
0:23:06 > 0:23:10So, the prairies and their sharks are surprising allies
0:23:10 > 0:23:13in the fight against a warming climate.
0:23:23 > 0:23:26The struggle to survive in our green seas
0:23:26 > 0:23:28can have far-reaching consequences.
0:23:30 > 0:23:37Once a year, one particular meadow in Australia is transformed.
0:23:44 > 0:23:47Around the first full moon of winter,
0:23:47 > 0:23:50an army materialises.
0:23:53 > 0:23:55Spider crabs.
0:24:03 > 0:24:06For the past year, they've been feeding in deeper waters.
0:24:17 > 0:24:21Now they march across the sea-grass plains.
0:24:39 > 0:24:42Hundreds of thousands of them.
0:24:50 > 0:24:52They clamber over one another...
0:24:59 > 0:25:01..creating great mounds...
0:25:07 > 0:25:09..nearly 100 metres long...
0:25:13 > 0:25:17They're not seeking mates, neither are they laying eggs.
0:25:17 > 0:25:20They have come here in order...
0:25:20 > 0:25:22to grow.
0:25:24 > 0:25:26Like all crabs,
0:25:26 > 0:25:27their bodies are enclosed
0:25:27 > 0:25:30in a hard, un-expandable shell.
0:25:33 > 0:25:36So, to grow, they have to break out of it...
0:25:46 > 0:25:52..and that allows the soft one that has developed beneath to expand.
0:26:00 > 0:26:02It will take days for the new shell to harden.
0:26:15 > 0:26:19Its legs are so limp that they won't work properly.
0:26:23 > 0:26:27The crab is unprotected and in great danger.
0:26:36 > 0:26:38A smooth stingray.
0:26:41 > 0:26:44It's huge - about four metres long.
0:26:46 > 0:26:50It wants a soft, freshly-moulted crab
0:26:50 > 0:26:52that will be easier to eat.
0:27:13 > 0:27:16The crabs try to stick together.
0:27:24 > 0:27:26But now, disturbed by the ray,
0:27:26 > 0:27:28they're scattering.
0:27:34 > 0:27:36A newly-moulted crab
0:27:36 > 0:27:39is too weak to keep up with the crowd.
0:27:46 > 0:27:49GRINDING
0:27:54 > 0:27:57The safest place is right in the middle of the pile.
0:27:59 > 0:28:02That is why they have all assembled here.
0:28:11 > 0:28:13There is safety in numbers.
0:28:29 > 0:28:32The vast majority of the crabs escape...
0:28:33 > 0:28:35..and within the next few days,
0:28:35 > 0:28:37they will be ready to return to the depths
0:28:37 > 0:28:42and resume their lonely wanderings in search of food.
0:28:54 > 0:28:56This is no graveyard...
0:28:59 > 0:29:04..but the triumph of a 100,000 crabs successfully moulted.
0:29:29 > 0:29:32The green seas of Southern Australia
0:29:32 > 0:29:36are particularly rich in such spectacular assemblies...
0:29:40 > 0:29:42..but most of the creatures come together
0:29:42 > 0:29:44for a very different reason.
0:29:46 > 0:29:48To breed.
0:29:52 > 0:29:54The giant cuttlefish,
0:29:54 > 0:29:57the largest of all cuttlefish.
0:30:05 > 0:30:07They live for just one or two years.
0:30:13 > 0:30:17Now, as the Australian summer draws to an end,
0:30:17 > 0:30:20they have one last act to complete.
0:30:24 > 0:30:25To find a mate.
0:30:31 > 0:30:34But there are over 100,000 males,
0:30:34 > 0:30:38competing for the arriving females in this one bay.
0:30:44 > 0:30:48Among them a giant - a true Goliath.
0:30:48 > 0:30:52He probably weighs about ten kilos.
0:30:54 > 0:30:58Bands of colour sweep across his skin.
0:30:58 > 0:31:00That's how cuttlefish communicate.
0:31:19 > 0:31:23This smaller male couldn't possibly take him on.
0:31:33 > 0:31:36Beside Goliath, and under his protection,
0:31:36 > 0:31:39a female who has just mated with him.
0:31:42 > 0:31:45But other rivals are still interested.
0:31:49 > 0:31:52It seems a small male wouldn't stand a chance.
0:31:54 > 0:31:57The female is now displaying a white stripe
0:31:57 > 0:32:00along her side nearest Goliath.
0:32:03 > 0:32:06It's a clear signal that she no longer wants to mate with him.
0:32:12 > 0:32:15It's all the encouragement that the little male needs.
0:32:38 > 0:32:41He's going to have to use trickery.
0:32:56 > 0:32:59He tones down his colours
0:32:59 > 0:33:01and tucks in his arms.
0:33:03 > 0:33:06He's just the right size to mimic a female.
0:33:17 > 0:33:19Goliath is deceived.
0:33:22 > 0:33:26The small male now displays a white stripe,
0:33:26 > 0:33:29just like the real female, to deter his advances.
0:33:36 > 0:33:37He slips beside her...
0:33:41 > 0:33:42..and they mate.
0:33:53 > 0:33:56By mating with multiple partners...
0:33:58 > 0:34:02..the female ensures the greatest genetic diversity for her young.
0:34:08 > 0:34:11The sneaky male leaves,
0:34:11 > 0:34:14his final act complete.
0:34:19 > 0:34:22So, even among giant cuttlefish, it seems...
0:34:25 > 0:34:27..it's not all about size.
0:34:38 > 0:34:42Other males in these Australian green pastures,
0:34:42 > 0:34:45take greater responsibility for their young.
0:34:54 > 0:34:57A weedy sea dragon.
0:35:04 > 0:35:08This is a male and he's carrying a precious cargo.
0:35:10 > 0:35:12While mating with the female,
0:35:12 > 0:35:16he collected the eggs and attached them to his underside.
0:35:22 > 0:35:25Now, he's leaving these seaweed thickets...
0:35:28 > 0:35:31..and travelling into more open waters
0:35:31 > 0:35:34where elaborate camouflage is less effective.
0:35:42 > 0:35:45And there are many predators out here.
0:36:06 > 0:36:11And this is what the fathers risk their lives for.
0:36:19 > 0:36:21Dense clouds of minute shrimp.
0:36:26 > 0:36:31Mysids, one of a sea dragon's favourite foods.
0:36:42 > 0:36:45They're drawing other sea dragons out here, too.
0:37:08 > 0:37:11Finally, it's time for the young to break free.
0:37:13 > 0:37:16But algae has grown over these developing eggs...
0:37:18 > 0:37:20..and it risks smothering them.
0:37:25 > 0:37:28Nonetheless, the babies are emerging.
0:37:39 > 0:37:41They've hatched successfully.
0:37:52 > 0:37:55The fathers return to the tangle of kelp,
0:37:55 > 0:37:57where they're virtually invisible...
0:38:04 > 0:38:06..while the young remain out here.
0:38:10 > 0:38:13But they will grow quickly,
0:38:13 > 0:38:16surrounded as they are by their ideal food.
0:38:27 > 0:38:30Vast numbers of the oceans' young fish
0:38:30 > 0:38:33start their lives in the green seas.
0:38:38 > 0:38:44One of the richest nurseries of all are the mangrove forests.
0:38:49 > 0:38:52Fringing the coastline of the tropics,
0:38:52 > 0:38:56they form a natural protective barrier between land and sea...
0:38:58 > 0:39:02..and are some of the world's most productive forests.
0:39:14 > 0:39:18Below the water, their arching aerial roots
0:39:18 > 0:39:20give them a firm footing.
0:39:31 > 0:39:34Here, there's abundant food for baby fish.
0:39:39 > 0:39:43While the tangled roots protect them from bigger fish
0:39:43 > 0:39:46and other predators that haunt the channels.
0:40:17 > 0:40:20But in Northern Australia,
0:40:20 > 0:40:22with the receding tide...
0:40:24 > 0:40:28..the little fish are forced to leave their shelter.
0:40:33 > 0:40:35And now, they are vulnerable.
0:41:21 > 0:41:25It's the most deadly assassin in the green seas.
0:41:32 > 0:41:35The zebra mantis shrimp -
0:41:35 > 0:41:39a male, almost 40 centimetres long.
0:41:56 > 0:41:59But he's not hunting just for himself.
0:42:04 > 0:42:08He's collecting food for his mate.
0:42:09 > 0:42:13She may have been his partner for 20 years.
0:42:21 > 0:42:24She relies on him to bring her food...
0:42:26 > 0:42:30..and puts her energy into her eggs instead.
0:42:35 > 0:42:37In a world so full of food,
0:42:37 > 0:42:39this would seem a sensible strategy.
0:42:47 > 0:42:49But it's also a risky one.
0:43:14 > 0:43:17Were her male to disappear,
0:43:17 > 0:43:19she could starve.
0:43:27 > 0:43:30Something has caught this male's attention.
0:43:32 > 0:43:35Perhaps an irresistible odour...
0:43:37 > 0:43:39..or a distant call.
0:43:41 > 0:43:43Whatever the reason,
0:43:43 > 0:43:46a male will leave his burrow
0:43:46 > 0:43:48and his lifelong mate.
0:43:57 > 0:44:00An even larger hole.
0:44:11 > 0:44:14Females who have lost their mates
0:44:14 > 0:44:18appear to send out distress signals to call in a new male.
0:44:25 > 0:44:28A larger female will produce more eggs.
0:44:28 > 0:44:32So by mating with her, he will father more offspring.
0:44:37 > 0:44:41But infidelity comes at a price.
0:44:44 > 0:44:48A larger partner demands more food.
0:45:02 > 0:45:06The richer a sea, the greater the competition..
0:45:07 > 0:45:09..and there is one green sea
0:45:09 > 0:45:14that supports more life than all the rest combined.
0:45:16 > 0:45:20Unlike the mangrove forests and the sea-grass prairies,
0:45:20 > 0:45:23its location is in the open seas
0:45:23 > 0:45:26and only temporary and unpredictable.
0:45:31 > 0:45:35This greenness comes not from rooted plants...
0:45:37 > 0:45:40..but from clouds of floating ones.
0:45:50 > 0:45:55Billions of microscopic phytoplankton are proliferating.
0:46:00 > 0:46:06And in such numbers that they fuel one of the greatest feasts of all.
0:46:15 > 0:46:18Off America's Pacific Coast,
0:46:18 > 0:46:22hundreds of common dolphins are rushing to a banquet.
0:46:22 > 0:46:24HIGH-PITCHED CLICKING
0:46:32 > 0:46:35They're not the only ones homing in.
0:46:37 > 0:46:39So are sea lions.
0:46:45 > 0:46:49They're heading for Monterey Bay, California,
0:46:49 > 0:46:54where algal blooms have caused an explosion
0:46:54 > 0:46:56in plankton feeders.
0:46:59 > 0:47:02Anchovies - millions of them.
0:47:09 > 0:47:12The dolphins herd the anchovies towards the surface.
0:47:15 > 0:47:20Sea birds and sea lions take advantage of the shoal's appearance.
0:47:24 > 0:47:28It's a race to grab a share before others arrive.
0:47:45 > 0:47:48DEEP RUMBLING
0:47:48 > 0:47:50Humpback whales,
0:47:50 > 0:47:53hundreds of them.
0:48:03 > 0:48:05With every upward lunge,
0:48:05 > 0:48:08they sieve out up to 100 kilos of fish.
0:48:25 > 0:48:27They're claiming the biggest share
0:48:27 > 0:48:31of one of the biggest feasts on Earth.
0:49:00 > 0:49:03So crucial are these tiny plankton,
0:49:03 > 0:49:07that almost all marine life ultimately depends upon them.
0:49:18 > 0:49:21It's the green seas, not the blue...
0:49:23 > 0:49:28..that are the basis of almost all life in the world's oceans.
0:50:17 > 0:50:20To capture the magnificence of the undersea forests
0:50:20 > 0:50:24and the surprising creatures living here, the Blue Planet II team
0:50:24 > 0:50:27have developed a series of specialist camera rigs.
0:50:35 > 0:50:39From the mega-dome recording half-in-half-out shots
0:50:39 > 0:50:41at the top of the towering canopy...
0:50:44 > 0:50:47..to state-of-the-art time-lapse equipment
0:50:47 > 0:50:51that speeds up time to reveal the secret life of the forest floor.
0:51:11 > 0:51:14But, of all the creatures living in these forests,
0:51:14 > 0:51:17filming one in the waters off the Cape of South Africa
0:51:17 > 0:51:19was to prove the greatest challenge of all.
0:51:22 > 0:51:26Naturalist Craig Foster has developed a fascination
0:51:26 > 0:51:30for its most secretive resident, a common octopus.
0:51:36 > 0:51:39There are almost 100 species of shark in these waters,
0:51:39 > 0:51:41but that doesn't deter Craig,
0:51:41 > 0:51:45who's swum here every morning for the past six years.
0:51:52 > 0:51:56When you find that really small, tiny, little oval hole,
0:51:56 > 0:51:59then you know it's been killed by an octopus.
0:52:00 > 0:52:02And then if you look very, very carefully,
0:52:02 > 0:52:06they're often in the vicinity of that.
0:52:13 > 0:52:16Craig has witnessed the antics of these octopuses
0:52:16 > 0:52:20and wants to share his remarkable discoveries
0:52:20 > 0:52:22with Blue Planet cameraman Roger Horrocks.
0:52:31 > 0:52:35Roger is immediately charmed by the strength of their personalities.
0:52:37 > 0:52:42It's really been astounding to see how individual these characters are.
0:52:42 > 0:52:45The common octopus all display different behaviours.
0:52:47 > 0:52:49Some were extremely timid,
0:52:49 > 0:52:51some were very, very bold,
0:52:51 > 0:52:54they have variety and it's really endeared me to them.
0:53:00 > 0:53:02After weeks of filming different individuals,
0:53:02 > 0:53:04they finally meet one octopus
0:53:04 > 0:53:08that's not only seemingly unafraid of the camera,
0:53:08 > 0:53:10but willing to perform for it.
0:53:20 > 0:53:22She just came right up - whoop!
0:53:22 > 0:53:24And then came right through underneath the tripod
0:53:24 > 0:53:25in between my legs.
0:53:25 > 0:53:27Yeah, that's cool, amazing.
0:53:27 > 0:53:31She very quickly just completely accepted both of us.
0:53:31 > 0:53:34So, we've actually been getting these really intimate behaviours.
0:53:34 > 0:53:36It's amazing.
0:53:40 > 0:53:42I've watched this octopus for many months,
0:53:42 > 0:53:44it's just trusting us in the water,
0:53:44 > 0:53:47carrying on with normal activity which is just so fantastic.
0:53:55 > 0:54:00Months later, the team finally film their star octopus on the hunt.
0:54:17 > 0:54:21But then discover the grave consequences of sharing the forest
0:54:21 > 0:54:23with so many other predators -
0:54:23 > 0:54:25pyjama sharks.
0:54:26 > 0:54:29Pound for pound, these sharks are far more brazen
0:54:29 > 0:54:31and aggressive than a Great White.
0:54:31 > 0:54:33They're like guided missiles.
0:54:33 > 0:54:38The slightest smell that octopus gives off, that shark will find it.
0:54:43 > 0:54:45The pyjama shark actually got hold of the octopus
0:54:45 > 0:54:48and, I mean, I just assumed that was it.
0:54:51 > 0:54:54After spending so much time with this animal,
0:54:54 > 0:54:57it was just so difficult watching her get attacked.
0:55:04 > 0:55:07Then, to their amazement, she fights back!
0:55:13 > 0:55:14She put her tentacles down,
0:55:14 > 0:55:17you can see them coming through the gill, basically,
0:55:17 > 0:55:19closed the mouth. The shark couldn't breathe,
0:55:19 > 0:55:21and that's what enabled her to escape.
0:55:21 > 0:55:24And just witnessing that whole thing was,
0:55:24 > 0:55:27you know, it was an incredibly intense moment.
0:55:29 > 0:55:32The team are relieved by her escape.
0:55:44 > 0:55:47But when caught out in the open,
0:55:47 > 0:55:50her next trick astonishes them even more.
0:55:53 > 0:55:56It lifted its arms and legs over its head,
0:55:56 > 0:56:00and, at the same time, pulled the shell material with it
0:56:00 > 0:56:03and created this extraordinary armoury.
0:56:05 > 0:56:08Octopus had armoured up and then, when that guy came
0:56:08 > 0:56:11through from the back, he could kind of smell something.
0:56:11 > 0:56:13He's not seeing an octopus shape,
0:56:13 > 0:56:16he's seeing that strange armoury.
0:56:16 > 0:56:19Then he was bumping the octopus,
0:56:19 > 0:56:22and it was just incredible to see how that octopus
0:56:22 > 0:56:24outwitted that shark using the armour,
0:56:24 > 0:56:26using all his, his knowledge,
0:56:26 > 0:56:29it's just...absolutely phenomenal.
0:56:34 > 0:56:37She's a rock star, man. A proper little rock star.
0:56:38 > 0:56:41Thanks to Craig's and Roger's dedication,
0:56:41 > 0:56:45the octopuses' astonishing behaviours are now known to science.
0:56:48 > 0:56:51What else might we find as we continue to explore
0:56:51 > 0:56:55these fascinating undersea forests?
0:57:00 > 0:57:03Next time on Blue Planet II...
0:57:03 > 0:57:06we meet the creatures that live where two worlds collide...
0:57:09 > 0:57:11..and discover how they cope with the demands
0:57:11 > 0:57:14of the ever-changing coasts.
0:57:24 > 0:57:27To find out more about our oceans with this free poster,
0:57:27 > 0:57:32call 0300 303 3520
0:57:32 > 0:57:37or go to bbc.co.uk/blueplanet2
0:57:37 > 0:57:40and follow the links to the Open University.