0:00:40 > 0:00:42An olive ridley turtle.
0:00:44 > 0:00:49She's resting in the shallows off Costa Rica...
0:00:52 > 0:00:55..having swum a thousand miles to be here.
0:01:05 > 0:01:11All because the eggs she carries must be laid on dry land.
0:01:18 > 0:01:21Now, she's returned to the very same beach
0:01:21 > 0:01:24where she hatched ten years ago.
0:01:32 > 0:01:37She must leave the safety of her marine world...
0:01:39 > 0:01:43..and brave the alien world beyond.
0:02:06 > 0:02:08She's heavily laden,
0:02:08 > 0:02:13but the future of the next generation of her kind is at stake.
0:02:20 > 0:02:25All along the beach, in a spectacle that has remained unchanged
0:02:25 > 0:02:31for millions of years, mother sea turtles emerge from the ocean...
0:02:34 > 0:02:36..in their hundreds of thousands.
0:02:49 > 0:02:53Only those animals that overcome the great challenges of both land
0:02:53 > 0:02:58and sea can make the most of life here on the coasts.
0:03:24 > 0:03:29Our shores are places of sudden changes and rich rewards.
0:03:33 > 0:03:38The Galapagos Islands in the tropical Pacific Ocean.
0:03:42 > 0:03:45Their barren coastline looks unhospitable,
0:03:45 > 0:03:50but one group of animals has learned to use it to their advantage.
0:04:01 > 0:04:04Sea lions.
0:04:07 > 0:04:09Bachelors.
0:04:10 > 0:04:15They need to pile on the pounds, as only the biggest males
0:04:15 > 0:04:17will attract a female and manage to breed.
0:04:22 > 0:04:26If these young bulls fail to grow big enough,
0:04:26 > 0:04:30they will remain exiled on this isolated shoreline.
0:04:38 > 0:04:42So, one hungry young bull heads out alone.
0:05:12 > 0:05:15He's on the hunt for big game.
0:05:23 > 0:05:25Yellowfin tuna.
0:05:28 > 0:05:31Each weighing 60kg...
0:05:33 > 0:05:36..with a top speed of 40mph.
0:05:39 > 0:05:43He can't possibly catch one in the open sea.
0:05:45 > 0:05:46But he has a plan.
0:05:49 > 0:05:52Ahead lies the entrance to the cove.
0:05:56 > 0:05:57He herds them towards it...
0:06:05 > 0:06:07..into his trap...
0:06:22 > 0:06:25..driving them into a dead end.
0:06:30 > 0:06:32But they give him the slip.
0:06:40 > 0:06:42He's failed.
0:06:47 > 0:06:49SEA LION BARKS
0:06:51 > 0:06:54But there might be another way.
0:07:12 > 0:07:16Now, they head off as a team...
0:07:18 > 0:07:20..to round up more tuna...
0:07:25 > 0:07:28..driving them back into the cove.
0:07:41 > 0:07:46The sea lions fan out, channelling the tuna towards the bottleneck.
0:08:04 > 0:08:07Once again, the tuna hit the dead end.
0:08:07 > 0:08:09But this time,
0:08:09 > 0:08:14the young bull doubles back to act as a blocker, sealing off the exit.
0:08:40 > 0:08:43This time when the shoal tries to escape, he blocks them
0:08:43 > 0:08:46and drives them back into the next blind alley.
0:09:00 > 0:09:03The gang can now pick them off one by one.
0:09:50 > 0:09:54This clever fishing technique, demanding foresight, planning
0:09:54 > 0:09:59and cooperation, has only ever been seen here in the Galapagos.
0:10:02 > 0:10:05Each massive fish provides them
0:10:05 > 0:10:09with five times more protein than a normal day's hunting.
0:10:13 > 0:10:17Finally, the young bull leaves his post...
0:10:20 > 0:10:22..to claim his reward.
0:10:37 > 0:10:39On a diet of protein-rich tuna,
0:10:39 > 0:10:44he's well on the way to becoming a full-sized breeding bull.
0:10:51 > 0:10:56By using this cove, these Galapagos sea lions have made the most
0:10:56 > 0:11:01of the opportunities that occur where the coast's two worlds meet.
0:11:10 > 0:11:15Coasts are the most swiftly changing of all ocean habitats
0:11:15 > 0:11:18because of the tides.
0:11:26 > 0:11:32Tides are created as the moon's gravity pulls at the sea.
0:11:42 > 0:11:47As the moon circles our planet, the seas rise and fall,
0:11:47 > 0:11:51typically twice a day,
0:11:51 > 0:11:57creating the most constantly dynamic landscapes on Earth.
0:12:06 > 0:12:12Nowhere else do sea-living creatures face such changeable conditions...
0:12:15 > 0:12:20..with the daily risk of drying out and being scorched by the sun.
0:12:27 > 0:12:29Where the tide retreats across a rocky shore,
0:12:29 > 0:12:33it can leave behind a temporary oasis.
0:12:41 > 0:12:42A rock pool.
0:12:53 > 0:12:56Seemingly, it's a haven of calm.
0:12:58 > 0:13:00But not for long.
0:13:02 > 0:13:07Turning minutes into seconds reveals unexpected dramas.
0:13:20 > 0:13:25In rock pools, grazers, scavengers and filter feeders
0:13:25 > 0:13:29must all make the most of the few short hours before the tide returns.
0:13:46 > 0:13:50Anemones gulp down anything they can reach...
0:13:52 > 0:13:55..though some meals are harder to digest than others.
0:14:04 > 0:14:09These magical worlds soon become battlegrounds.
0:14:12 > 0:14:15A deadly predator with five arms
0:14:15 > 0:14:18and, on the underside, a mouth.
0:14:22 > 0:14:23The ochre starfish.
0:14:28 > 0:14:31And it's in search of limpets.
0:14:50 > 0:14:55For some, there is no escape. It engulfs them.
0:15:02 > 0:15:06But other limpets have a secret defence.
0:15:08 > 0:15:11They deploy a slippery shield...
0:15:13 > 0:15:17..which allows them to slide to safety.
0:15:21 > 0:15:25And this limpet has its own personal bodyguard.
0:15:35 > 0:15:38A scale worm with a nasty nip.
0:15:43 > 0:15:47The starfish prefers food that doesn't bite back.
0:15:49 > 0:15:55The limpet carries on, its bodyguard tucked safe under its shell.
0:15:58 > 0:16:03But there is one creature the limpets have no defence against.
0:16:05 > 0:16:07A clingfish.
0:16:09 > 0:16:12It has teeth that can lever under the shell
0:16:12 > 0:16:17and twist the limpet off like a bottle top.
0:16:21 > 0:16:26The clingfish then swallows it, shell and all.
0:16:34 > 0:16:37Rock pool dramas like these
0:16:37 > 0:16:41last just a few short hours before the tide returns.
0:16:45 > 0:16:50Every day, the sea becomes land and the land becomes sea...
0:16:58 > 0:17:00..bringing new opportunities.
0:17:04 > 0:17:06A Sally Lightfoot crab.
0:17:09 > 0:17:14One of thousands of shore crabs just waiting for their moment.
0:17:17 > 0:17:21Every day, they gather on the tropical shores of Brazil...
0:17:24 > 0:17:25..waiting for the tide to go out...
0:17:35 > 0:17:38..which exposes their feeding grounds -
0:17:38 > 0:17:43seaweed-covered rocks 100m from the shore.
0:17:52 > 0:17:56Getting there is a race against the tide.
0:18:02 > 0:18:05They leap from rock to rock.
0:18:19 > 0:18:22These crabs seem to be afraid of the water.
0:18:34 > 0:18:36And for good reason.
0:18:48 > 0:18:50The moray eel.
0:18:52 > 0:18:57The chain moray is a specialist crab hunter.
0:19:02 > 0:19:07Its blunt teeth can easily grip and crush a crab's shell.
0:19:12 > 0:19:15It's the crabs' deadliest enemy.
0:19:26 > 0:19:29But the crabs' feeding grounds are still a long way off.
0:19:35 > 0:19:38They must press on.
0:20:00 > 0:20:01Halfway.
0:20:06 > 0:20:10But their enemy has other ideas.
0:20:15 > 0:20:17Crossing the land...
0:20:23 > 0:20:26..to reset the ambush.
0:20:29 > 0:20:33To feed, the crabs must keep going.
0:20:38 > 0:20:41But nowhere is safe.
0:20:45 > 0:20:47An octopus, also a crab killer.
0:21:13 > 0:21:16The crabs make a dash for it.
0:21:42 > 0:21:44Made it!
0:21:53 > 0:21:57Risking life and limb to graze on these seaweed pastures.
0:22:01 > 0:22:05But in two hours' time when the tide starts to turn,
0:22:05 > 0:22:09they will have to run the gauntlet all over again.
0:22:19 > 0:22:23Tides are not the only force to have an impact on the coasts.
0:22:43 > 0:22:47The greatest waves originate far out to sea
0:22:47 > 0:22:51and roll in towards the coast, growing as they come.
0:23:03 > 0:23:07As the shallowing sea floor drags their underside,
0:23:07 > 0:23:14their crests rise up to 100ft high, topple over and break.
0:23:22 > 0:23:24Many of the biggest surfed waves in the world
0:23:24 > 0:23:27are formed off Nazare in Portugal.
0:23:43 > 0:23:46Every day along this coast, the impact of the waves
0:23:46 > 0:23:51is equivalent to one and a half million tonnes of TNT.
0:24:13 > 0:24:18Wave power gradually moulds and reshapes our coasts.
0:24:22 > 0:24:24In some parts of Europe,
0:24:24 > 0:24:29waves wear away as much as three metres of coastline each year.
0:24:36 > 0:24:41The rate at which the waves reshape the rock depends on its hardness.
0:24:42 > 0:24:48Where soft rock lies below hard, dramatic arches are carved.
0:25:05 > 0:25:08It's an endless assault that gradually sculpts
0:25:08 > 0:25:13vaulted cathedrals of stone, as here in northern Spain.
0:25:25 > 0:25:28And wave power creates towering fortresses,
0:25:28 > 0:25:30like these cliffs in the Arctic,
0:25:30 > 0:25:34home to tens of thousands of breeding sea birds.
0:25:39 > 0:25:42The faces of the cliffs are accessible only from the air
0:25:42 > 0:25:45and have plenty of nooks and crannies
0:25:45 > 0:25:47for those that can get there.
0:25:51 > 0:25:57But to feed, sea birds must still master the ocean world beyond.
0:26:01 > 0:26:03The puffin.
0:26:07 > 0:26:10He's a fisherman and a father.
0:26:15 > 0:26:18He has a mate for life.
0:26:24 > 0:26:28Both share the burden of raising their week-old chick,
0:26:28 > 0:26:33their puffling, who needs five square meals a day.
0:26:35 > 0:26:38The parents alternate fishing trips.
0:26:41 > 0:26:44It's Dad's turn.
0:27:06 > 0:27:11When fish stocks are low, puffins must fly as much as 30 miles
0:27:11 > 0:27:16out to sea to reach the good fishing grounds.
0:27:28 > 0:27:32Once there, they plunge into another world.
0:27:40 > 0:27:44Good fishing spots are hard to come by...and they have company.
0:27:46 > 0:27:48Guillemots.
0:27:55 > 0:27:59Like the puffin, their wings are short and good for diving.
0:28:01 > 0:28:05Puffins can hold their breath for over a minute
0:28:05 > 0:28:08and dive as deep as 40m.
0:28:13 > 0:28:15A catch!
0:28:33 > 0:28:36But it's a long way home.
0:28:49 > 0:28:54After an exhausting round trip of almost 60 miles,
0:28:54 > 0:28:56this puffin's nearly made it.
0:28:58 > 0:29:01But there are pirates on this coast.
0:29:04 > 0:29:06Arctic skuas.
0:29:31 > 0:29:35All around, returning parents are being robbed.
0:30:00 > 0:30:04The skuas' long, raked back wings
0:30:04 > 0:30:06make them faster and more manoeuvrable.
0:30:44 > 0:30:47Puffins must choose their moment wisely.
0:31:08 > 0:31:09A near miss.
0:31:27 > 0:31:30The last desperate burst of speed...
0:31:32 > 0:31:34..and it's made it.
0:32:00 > 0:32:04Safely home after a three-hour round trip...
0:32:11 > 0:32:14..where his patient partner is waiting.
0:32:30 > 0:32:33Today, their puffling will eat.
0:32:40 > 0:32:42But where fish numbers are in decline,
0:32:42 > 0:32:48many puffins now find it hard to get enough food for their chicks.
0:32:50 > 0:32:51In the changing seas of today,
0:32:51 > 0:32:56it can be even harder to be a successful puffin parent.
0:33:07 > 0:33:11Overcoming the challenges of two worlds is seldom easy.
0:33:12 > 0:33:17One marine creature has virtually abandoned the sea altogether.
0:33:20 > 0:33:23On a few remote Pacific islands
0:33:23 > 0:33:27lives the most terrestrial fish on the planet.
0:33:32 > 0:33:36At the top of this metre-high limestone cliff...
0:33:40 > 0:33:44..an eight-centimetre-long blenny has chosen a nest hole.
0:33:50 > 0:33:54Up here, he can graze on the abundant algae
0:33:54 > 0:33:57without any competition from seagoing fish.
0:33:58 > 0:34:01The females are feeding beneath him.
0:34:05 > 0:34:08He's keen to attract their attention.
0:34:11 > 0:34:14But they are busy moisturising.
0:34:14 > 0:34:18Staying damp is essential as they breathe through their skins.
0:34:23 > 0:34:27To make himself conspicuous, he turns black...
0:34:31 > 0:34:34..and flashes his orange fin.
0:34:35 > 0:34:37He catches her eye.
0:34:40 > 0:34:46But these Pacific leaping blennies seem afraid of the waves.
0:34:49 > 0:34:51They're poor swimmers
0:34:51 > 0:34:54and would be easy prey in the sea.
0:34:57 > 0:34:59Time to try again.
0:35:02 > 0:35:04She's tempted.
0:35:08 > 0:35:12But, once again, distracted by a wave.
0:35:35 > 0:35:39The male just won't give up.
0:35:50 > 0:35:53Finally, she's hooked.
0:35:56 > 0:35:59He makes way...
0:36:01 > 0:36:04..so she can enter his cave.
0:36:07 > 0:36:14And he encourages her to lay her eggs with his seductive dance.
0:36:27 > 0:36:32He then fertilises them in the safety of his nest.
0:36:43 > 0:36:46The blenny has given up the sea for a life on land.
0:36:49 > 0:36:53Others have made an even more successful move,
0:36:53 > 0:36:55but in a different direction.
0:37:02 > 0:37:05Penguins have abandoned flying
0:37:05 > 0:37:09and instead spend most of their lives swimming.
0:37:10 > 0:37:14Their sleek survival suits of tightly packed feathers
0:37:14 > 0:37:16are perfect for these freezing waters.
0:37:18 > 0:37:22Yet they must still come ashore once a year.
0:37:35 > 0:37:40South Georgia - an island wilderness close to Antarctica.
0:37:51 > 0:37:54Each spring, its beaches become the busiest on Earth
0:37:54 > 0:37:59as hundreds of thousands of king penguins return here.
0:38:08 > 0:38:10They're heading for the colony.
0:38:16 > 0:38:21But in their way lies the biggest wall of blubber on the planet.
0:38:25 > 0:38:27Elephant seals.
0:38:35 > 0:38:37It's the breeding season
0:38:37 > 0:38:40and the four-tonne bulls are fighting
0:38:40 > 0:38:42for control of their harems.
0:38:45 > 0:38:48Best to wait for them to calm down.
0:39:03 > 0:39:05He can't fly over this barrier
0:39:05 > 0:39:09so he will have to walk as unobtrusively as possible...
0:39:12 > 0:39:17..and hope that sleeping giants will continue to lie.
0:39:28 > 0:39:30Careful!
0:39:47 > 0:39:50This could be tricky.
0:40:08 > 0:40:10A rival bull mounts a challenge.
0:40:12 > 0:40:15The penguins could be caught in the crossfire.
0:40:46 > 0:40:49Eight tonnes of blubber collide.
0:41:10 > 0:41:14The towering beach master is victorious.
0:41:20 > 0:41:24In the confusion, this penguin slips through.
0:41:26 > 0:41:30Ahead are 40,000 chicks...
0:41:33 > 0:41:37..hungry and overexcited.
0:41:52 > 0:41:55But not every penguin has a chick to feed.
0:41:55 > 0:41:57That's not why they're here.
0:42:01 > 0:42:04There is another reason.
0:42:05 > 0:42:10There is a trial of endurance that every penguin must face.
0:42:11 > 0:42:15And it starts with a persistent itch.
0:42:21 > 0:42:26His survival suit has been worn thin by months of swimming
0:42:26 > 0:42:28in the rough Southern Ocean.
0:42:29 > 0:42:32His solution is drastic.
0:42:36 > 0:42:40Shed all four layers of feathers as quickly as possible.
0:42:45 > 0:42:48The process is known as a catastrophic moult.
0:42:54 > 0:42:57Until their feathers regrow,
0:42:57 > 0:43:00penguins will remain rooted to the spot.
0:43:23 > 0:43:27Having starved for a month, they're now fully waterproofed
0:43:27 > 0:43:30and insulated once more...
0:43:44 > 0:43:50..lean, hungry and eager to return to a life at sea.
0:44:06 > 0:44:09Thanks to their waterproof plumage,
0:44:09 > 0:44:12penguins are able to make the most of both worlds,
0:44:12 > 0:44:15even in some of the harshest conditions on Earth.
0:44:31 > 0:44:34The coasts of South Georgia are currently protected
0:44:34 > 0:44:37by their remoteness.
0:44:38 > 0:44:41Other coastlines are much more vulnerable.
0:44:46 > 0:44:50And they are now changing faster than ever before.
0:44:54 > 0:44:59Two-thirds of our major cities are on our coasts.
0:45:01 > 0:45:04It's estimated that in the next decade,
0:45:04 > 0:45:08we can expect 10% of the world's remaining wild shores
0:45:08 > 0:45:12to be taken over by human development.
0:45:20 > 0:45:24Yet every year, just off Florida's Palm Beach,
0:45:24 > 0:45:28an extraordinary spectacle appears almost unnoticed.
0:45:35 > 0:45:40The biggest gathering of coastal sharks on the planet.
0:45:44 > 0:45:47Spinners and blacktips.
0:45:52 > 0:45:5410,000 of them.
0:46:04 > 0:46:09Every January, they seek out these warm shallows as a stopover
0:46:09 > 0:46:13on their migration northwards.
0:46:17 > 0:46:23Sharks have been gathering here since long before people arrived.
0:46:33 > 0:46:37But today, they face levels of pollution
0:46:37 > 0:46:41and habitat degradation as well as fishing pressures
0:46:41 > 0:46:45that their ancestors would never have experienced.
0:46:48 > 0:46:52It's no longer enough for coastal creatures
0:46:52 > 0:46:55to master their own worlds.
0:47:02 > 0:47:05Now, they must face the many challenges
0:47:05 > 0:47:08that come from our world, too.
0:47:31 > 0:47:33To film the most surprising coastal wildlife,
0:47:33 > 0:47:35the Blue Planet II team travelled
0:47:35 > 0:47:38to some of the remotest shores on the planet.
0:47:41 > 0:47:45One destination was the Galapagos Islands.
0:47:46 > 0:47:49Here, they were in search of an almost unbelievable story,
0:47:49 > 0:47:53brought to them by a local cameraman, Richard Wollocombe.
0:47:53 > 0:47:55Well, I was talking to a friend of mine
0:47:55 > 0:47:57who's a fisherman over here and he said
0:47:57 > 0:48:00that one day, he'd turned up here in this bay
0:48:00 > 0:48:04and suddenly he saw a group of sea lions
0:48:04 > 0:48:07chasing these massive tuna up onto the beach
0:48:07 > 0:48:11and I was just like, "Yeah, funny one. I don't believe a word of that.
0:48:11 > 0:48:13"That just sounds too unreal."
0:48:13 > 0:48:18Still, the lure of the fisherman's tale was too great to ignore.
0:48:18 > 0:48:22I'm a little nervous. If it doesn't happen, there goes my credibility.
0:48:25 > 0:48:28The Blue Planet II team launch a full-scale expedition.
0:48:31 > 0:48:33But one of them is still sceptical.
0:48:33 > 0:48:36It's going to be pretty spectacular
0:48:36 > 0:48:40if a sea lion could actually chase down and kill a tuna.
0:48:40 > 0:48:42I'm still yet to be convinced.
0:48:43 > 0:48:49They set up camp in this barren cove, home for the next month.
0:48:51 > 0:48:54The local wildlife, famed for its tameness,
0:48:54 > 0:48:57is curious to meet its new neighbours.
0:48:57 > 0:48:59Shoo! Shoo!
0:49:01 > 0:49:03Shoo, shoo, shoo!
0:49:03 > 0:49:05Shoo, shoo!
0:49:08 > 0:49:10With no sign of the sea lions,
0:49:10 > 0:49:15the crew stake out the cove with remote underwater cameras.
0:49:17 > 0:49:21Field assistant Roby Pepolas takes first watch.
0:49:21 > 0:49:26This is the point of view where we try to see the sea lions coming,
0:49:26 > 0:49:27jumping over the water.
0:49:27 > 0:49:32If they are definitely coming very close, I say, "Action! Action!"
0:49:32 > 0:49:35- Or, "Rock and roll!" - HE LAUGHS
0:49:37 > 0:49:38Three hours later...
0:49:40 > 0:49:41Richard!
0:49:41 > 0:49:44HE SHOUTS IN SPANISH
0:49:45 > 0:49:48The aerial team are first up.
0:49:51 > 0:49:54It's a sea lion chasing tuna into the bay.
0:50:08 > 0:50:11Oh, he's got it! He's got it!
0:50:11 > 0:50:15Unbelievable! Look at that, it's still struggling!
0:50:15 > 0:50:17Holy Moley!
0:50:18 > 0:50:20He's lost him.
0:50:20 > 0:50:23The tuna gives the sea lion the slip.
0:50:29 > 0:50:32Over the coming days, more sea lions arrive in the cove,
0:50:32 > 0:50:34chasing in yellowfin tuna.
0:50:37 > 0:50:39Yeah, yeah, yeah, yeah, yeah. Ooh!
0:50:39 > 0:50:43Richard, there's more tuna and another sea lion.
0:50:43 > 0:50:45There's, like, six tuna in the bay.
0:50:54 > 0:50:57One sea lion has caught Richard's attention
0:50:57 > 0:51:00and he has affectionately called him Tag Boy.
0:51:01 > 0:51:06He's really different. He's, like, a prolific hunter. He's really agile.
0:51:06 > 0:51:08It's just fascinating to watch
0:51:08 > 0:51:12and see the picture emerge about who he is.
0:51:13 > 0:51:16From above, the drone is revealing
0:51:16 > 0:51:18how the group of sea lions are hunting together.
0:51:18 > 0:51:21From the air, we really see the strategy of the sea lions
0:51:21 > 0:51:23and see them with their individual roles as well.
0:51:23 > 0:51:26Tag Boy stays off in the middle of the channel to make sure
0:51:26 > 0:51:27none of them escape.
0:51:27 > 0:51:29Everyone's got a role and they're really a team
0:51:29 > 0:51:31in bringing them together.
0:51:31 > 0:51:34Although the sea lions have been hunting in the shallows,
0:51:34 > 0:51:39the crew are yet to see them drive a tuna onto the beach.
0:51:40 > 0:51:45And to make matters worse, the sea lions aren't alone in this cove.
0:51:52 > 0:51:55Galapagos sharks, each two metres long.
0:51:58 > 0:52:01The shark almost beached itself
0:52:01 > 0:52:08and stole the tuna from the big sea lion, who is now really angry.
0:52:09 > 0:52:12Despite the sharks, to reveal the full story,
0:52:12 > 0:52:15Richard needs to get in the water.
0:52:15 > 0:52:18Classic shark attack scenario - blood in the water,
0:52:18 > 0:52:21shallow and easy mistaken identity.
0:52:28 > 0:52:30Watch your hands, Roby.
0:52:30 > 0:52:31The crew gain
0:52:31 > 0:52:34some protection from chainmail suits.
0:52:43 > 0:52:47There's a lot of sharks. One, two, three, four, five, six sharks now.
0:52:49 > 0:52:53With so much blood in the water, the sharks go into a feeding frenzy.
0:53:07 > 0:53:10They make mincemeat of these tuna in seconds.
0:53:10 > 0:53:11To be so close to something
0:53:11 > 0:53:15so unbelievably ferocious and dangerous,
0:53:15 > 0:53:18quite frankly, is amazing.
0:53:18 > 0:53:21It's nice to be able to hide behind all this, though.
0:53:24 > 0:53:27But then, after a week of increasing activity,
0:53:27 > 0:53:30the sea lions suddenly stop fishing.
0:53:36 > 0:53:39It's the first day that we haven't seen action during the whole day
0:53:39 > 0:53:42since we start.
0:53:42 > 0:53:43I kind of worry.
0:53:45 > 0:53:47The tuna have disappeared.
0:53:59 > 0:54:01Richard is worried.
0:54:01 > 0:54:04The science is starting to show, across the globe,
0:54:04 > 0:54:07that the seas are warming, they're becoming less productive.
0:54:07 > 0:54:12Galapagos marine life relies on cold, deep currents
0:54:12 > 0:54:16welling up intermittently to fertilise the surface waters.
0:54:18 > 0:54:20If those upwellings become less consistent,
0:54:20 > 0:54:24their lives could yet well be in jeopardy.
0:54:24 > 0:54:25In the past,
0:54:25 > 0:54:28when these cold water upwellings have temporarily stopped,
0:54:28 > 0:54:31many sea lions have starved to death
0:54:31 > 0:54:37and a warming ocean could further weaken these upwellings.
0:54:42 > 0:54:46Then, after two weeks of nervous waiting, a hopeful sign -
0:54:46 > 0:54:50a thick fog descends over the cove.
0:54:50 > 0:54:53We've got very cold water that's come up, upwelled,
0:54:53 > 0:54:56and spread across the ocean and mixed with the warm air,
0:54:56 > 0:54:59creating the fog and we're hoping that this cold water
0:54:59 > 0:55:04will just kick things off a bit and get the action going.
0:55:04 > 0:55:08As the fog clears, a welcome sight.
0:55:08 > 0:55:12The tuna are back with sea lions hot on their heels.
0:55:15 > 0:55:17The crew leap into action.
0:55:22 > 0:55:23HE SPEAKS IN SPANISH
0:55:25 > 0:55:31Being in the water, Richard can at last follow the sea lions' teamwork.
0:55:35 > 0:55:39And finally film Tag Boy beaching a tuna.
0:55:41 > 0:55:43They know the bottlenecks in this labyrinth.
0:55:43 > 0:55:46They know how to push them into those bottlenecks
0:55:46 > 0:55:50and Tag Boy, almost his entire body was blocking the entrance,
0:55:50 > 0:55:54and he was just gently back and forth, tiring the fish out.
0:55:54 > 0:55:57Absolutely extraordinary, really, really impressive.
0:55:57 > 0:56:02Director Rachel has a new-found respect for the sea lions.
0:56:02 > 0:56:06I had no idea they were capable of this level of planning
0:56:06 > 0:56:10and strategy and teamwork.
0:56:10 > 0:56:12I had no idea they were this intelligent.
0:56:14 > 0:56:18Richard has succeeded in filming this unique hunting strategy
0:56:18 > 0:56:23and in doing so has proved the fisherman's tale to be true.
0:56:23 > 0:56:27The sea lions' intelligence is unbelievably sophisticated
0:56:27 > 0:56:30so to say that my expectations have been exceeded
0:56:30 > 0:56:32is a slight understatement.
0:56:32 > 0:56:34This has been one of the most remarkable times
0:56:34 > 0:56:35I've ever had here in the Galapagos.
0:56:46 > 0:56:49Next time, we travel the world
0:56:49 > 0:56:53to uncover the biggest issues facing the ocean...
0:56:55 > 0:56:59..meet the passionate people who've devoted their lives
0:56:59 > 0:57:01to protecting it
0:57:01 > 0:57:06and discover what the future holds for our Blue Planet.
0:57:10 > 0:57:14To find out more about our oceans with this free poster, call...
0:57:23 > 0:57:26..and follow the links to the Open University.