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00:00Ours is truly a magical place.
00:28Ours is truly a blue planet.
00:35Water covers most of the world's surface.
00:44Here we are the outsiders.
00:59But under the waves, one group thrives.
01:06Fish.
01:14Fish are masters of the waters.
01:22And sailfish are the fastest of them all.
01:27Their speed makes them one of the ocean's most fearsome predators.
01:35Off the coast of Mexico, 30 sailfish have surrounded a ball of sardines.
01:48To catch their prey requires more than speed alone.
01:57In the tightest turns, fins maintain stability.
02:01Their sickle-shaped tail powers them forwards, and that extraordinary dorsal fin helps intimidate
02:08their prey.
02:18To the naked eye, the action is too fast.
02:21Slowed, their challenge becomes clear.
02:26Just picking a target is hard enough.
02:31Stalking it off balance separates it from the show.
02:36This requires extraordinary skill.
02:50Not every attempt is successful.
03:15But as more sailfish join in, when one misses, another takes its place.
03:30The shoal of sardines is methodically wiped out.
03:39Sailfish are top predators.
03:41Very little threatens them.
03:43But for the majority of fish, this is not the case.
03:51For most fish, the open ocean is extremely dangerous.
03:58And some go to extraordinary lengths just to survive.
04:15Flying fish.
04:22Free of the water, they soar on elongated fins, leaving their predators far behind.
04:50A flight of fish.
04:57Escaping predators is not the only test facing the flying fish.
05:05They must also protect their developing young.
05:12These flying fish are searching for the one thing that will make this possible.
05:19In such a vast ocean, it's not easy.
05:23They're in luck.
05:27A palm frond.
05:32It's a tiny island, adrift in a huge ocean.
05:39And like an island, it offers shelter not for the flying fish, but for their eggs.
05:48The females lay eggs on the raft, where the males fertilize them.
06:00The first fish spawn, and this triggers the others to start.
06:16Soon, thousands join the melee.
06:23Innumerable strands of eggs are laid.
06:29The raft starts to tilt under their weight.
06:49The best place to lay eggs is right inside the frond.
07:04For some, the attempt proves fatal, and living fish become entombed.
07:21The raft starts to sink under the weight of so many eggs.
07:30This is far from a disaster.
07:33Sinking away from the surface actually improves the eggs' chances of survival.
07:39In just a few days, having been safely hidden in the depths, they'll hatch out.
07:49Other fish protect their offspring in different ways.
07:53Some go to far greater lengths to care for them.
08:09The shallow waters of southern Australia are home to many strange creatures.
08:26It's a fairytale world of seahorses, stargazers, and stingrays, but none compare with the beauty
08:48of the weedy sea dragon.
09:02The dragon's tiny fins beat frantically to prevent the current from sweeping it away.
09:20It's the beginning of spring, the season when sea dragons begin their courtship.
09:35And in the evening light, they start to dance.
09:58In a graceful duet, each partner mirrors the actions of the other.
10:26Darkness will soon draw a veil over the pair, but they will dance on into the night.
10:54Two months later, and the result of their courtship is revealed.
11:15It's the male, and he's the one that's carrying the eggs, with rows and rows of them embedded
11:22in his tail.
11:26That night, the female transferred her eggs to him.
11:31Since then, the male alone has cared for them.
11:35By carrying them with him, he's kept them safe.
11:49And now, it's time for his efforts to be rewarded.
11:57The eggs are ready to hatch.
12:11In the calm of a summer morning, a baby sea dragon with yolk sacs still attached is born.
12:27The weed bed shelters older dragons that are already able to feed themselves.
12:44Although these dragons were well cared for by their father, now they must find their
12:48own way in the world.
12:55There are fish, however, which provide their young with a safe refuge for far longer.
13:05The southwestern Pacific.
13:10A convict fish, and it's something of a marine architect.
13:17Underground, it has created a labyrinth of tunnels.
13:23This adult never ventures out of its burrow.
13:27What it eats is a mystery.
13:35But it doesn't live here alone.
13:39At another entrance, faces peer out.
13:43Juvenile convict fish.
13:48Unlike their parent, the youngsters are not tied to the burrow.
13:56And as they start to emerge, a trickle becomes a flood of fish.
14:04There are thousands of them.
14:14And they all help with the chores.
14:30Only hands make light work.
14:54The young fish swarm together, thousands of mouths gulping plankton.
15:10What the adults eat must somehow involve these youngsters.
15:17Whether the young feed their parents by regurgitating food, or through some other mechanism, we
15:23just don't know.
15:26Whatever the answer, the youngsters provide their parents with a meal, and in return get
15:31a roof over their heads.
15:45Producing young is just one challenge.
15:48Providing food and somewhere to live are further trials fish must face.
15:57The Californian coast.
15:58A wide range of species live here.
16:03But all this life means competition for living space is intense.
16:22Old shells are highly prized.
16:28This one is occupied by a sarcastic fringe head.
16:34These fish are exceptionally quarrelsome.
16:38They have to be to defend their living space.
16:58An octopus.
17:03Inadvertently, it's wandered into the fringe head's territory, and that can't be tolerated.
17:27The octopus's impressive jab holds the fringe head at bay.
17:41There is more to this behavior than being bad-tempered.
17:47The fringe head needs to defend its patch if it is to get enough to eat, and the octopus
17:52was competition.
18:04Crabs are not the easiest of mouthfuls.
18:10Because of the shortage of living space, there are constant boundary disputes, especially
18:17with other fringe heads.
18:20This one has got too close.
18:29Despite the most extravagant threats, neither is prepared to back down.
18:59Success, and it's quick to get back to its shell.
19:09A fringe head can never drop its guard.
19:12There's too much competition.
19:20Some fish have moved to places where they have fewer rivals.
19:38A mudskipper, a fish that spends most of its life out of the sea.
19:46It can walk on land and breathe air.
19:52Its life is very different from that of most fish.
20:00A fish out of water, maybe, but they thrive here in Japan.
20:11So what's made this upheaval worthwhile?
20:16The answer lies in the mud.
20:22As the tide retreats, it exposes mud flats.
20:28Sunlight hits the rich silt and tiny plants and animals flourish there.
20:35All food for a mudskipper.
20:39But life on land is not without problems.
20:42It's hard work to find a mate.
20:54Diving high above the mud will get you noticed.
21:15With eyes perched on the top of their heads, the mudskippers keep a lookout for both friend
21:21and foe.
21:24And males fight those who intrude on their territory.
21:48They must also take care not to dry out in the sun.
21:55Rolling in the ooze keeps the skin cool and moist.
22:03For this smaller species, a better option is to retreat underground.
22:15So he digs himself a tunnel down into the mud.
22:32This heap of spoil is an indication of the extent of his excavations.
22:52With the tide flooding the tunnel twice a day, maintenance is a real burden.
23:05The tunnel is more than a refuge from the sun.
23:08It serves another very important purpose.
23:12The tunnel is actually U-shaped, and at the far end is a sealed chamber, the walls of
23:18which are lined with eggs.
23:24The eggs are kept in air, as it's richer in oxygen than the water.
23:30The problem is the air that's trapped here won't last for long.
23:34So the male travels to the open end of the tunnel to gulp fresh air.
23:40Back he goes down his tunnel, where he releases it into the egg chamber.
23:47Replenishing the oxygen on which the eggs depend.
23:54He will repeat this hundreds and hundreds of times until his young hatch.
24:05This lifestyle is very demanding, yet the mudskipper has found a way around every problem.
24:19The harsh challenges of life in the ocean have encouraged other fish to leave the sea.
24:26Not for land, but for fresh water.
24:31Hawaii is the remotest island chain on the planet.
24:37These pools look the perfect place for the fish to live, secluded and free from competition
24:43and predators.
24:46Yet few contain fish, for one very considerable reason.
25:01Surely no fish could swim up this.
25:18But one fish comes from the ocean intent on colonising these streams.
25:28It's a tiny goby, and it's a rock climber.
25:36With pelvic fins fused into a disc, which acts like a sucker, all the goby needs is
25:42a film of water to climb through.
25:54The pioneer is soon followed by many others, possibly following its scent trail.
26:12They clamber on, ever upwards, against the flow.
26:31Drops of water fall like bombs.
26:47False leads waste crucial energy.
26:54Some must rest.
26:58For others, the effort is just too much.
27:09They die in their attempt to reach the top.
27:34Against all the odds, a few heroic individuals do make it to the top.
27:51They find themselves in a near-perfect fish habitat.
28:03Where the gobies can feed and grow and breed in peace.
28:12In time, their own young will be swept downstream and out to sea, and the cycle will begin all
28:18over again.
28:34Fresh water presents particular challenges for fish.
28:40Nutrients can be in very short supply in spring water, so here fish must take every chance
28:46they can to find food.
28:48The rain that falls on these Kenyan hills percolates through the rocks, finally emerging
28:57as crystal-clear pools.
29:07Pools that are home to fish, including barbel.
29:15The fish share these waters with all sorts of creatures.
29:30Including hippopotamus.
29:42These giant vegetarians are no threat to the fish.
29:46In fact, they're key to their survival here.
29:56After a night of grazing on land, these hippos return to spend the daylight hours in the
30:02cooling waters.
30:18And the barbel come to meet them.
30:28Then each hippo is trailed by a shoal of fish, waiting for their breakfast.
30:37Hippo droppings.
30:47But it's not just the hippos' dung the fish are interested in.
30:50When the hippos reach one particular spot in the pool, they stand still and wait.
31:05And the fish start to clean them, removing ticks and parasites and other tasty morsels.
31:19To the fish, the hippos are a mobile cafeteria.
31:28The hippos seem to be enjoying the sensation.
31:34The only thing that interrupts the feast is the need to take an occasional breath.
31:49Cleaning the hippo's skin was just the hors d'oeuvre.
31:53Now it's time for the main course.
32:03So in addition to providing skin care, the fish look after the hippo's dental hygiene.
32:10It's an arrangement that suits both parties.
32:20But perhaps it's the fish that are the overall winners.
32:25For thanks to the hippos, they are able to feed on the abundant vegetation that would
32:30otherwise be beyond their reach, growing around their pool on land.
32:39Providing a cleaning service is clearly a good way of getting a meal.
32:45And there is cleaning to be done in the sea as well.
33:04The life of this wrasse is centred on removing parasites from other reef fish,
33:14including predatory jacks.
33:23Normally they would snap up such a little fish, but this is an established relationship
33:29and both sides know the rules.
33:36With so many jacks and only a few wrasse in attendance, not all the jacks are going to
33:41get cleaned.
33:47But all this life attracts other predators, silvertip sharks.
34:11The reef provides shelter for the smaller fish, but the jacks remain exposed.
34:16Yet this may be a chance for the jacks to solve their cleaning problem.
34:23They've spotted an opportunity.
34:42Sharks have skin like sandpaper, and bumping into the shark's flanks helps the jacks to
34:50rid themselves of parasites and dead skin.
34:54Perhaps the jacks find this a more effective alternative to the cleaner fish.
35:01And soon, swarms of jacks pursue the sharks, all itching to have a scratch.
35:12Unsurprisingly, all this attention bothers the sharks, and they head back to the blue
35:20water, leaving the residents of the reef to resume life as normal.
35:36Coral reefs are the richest habitats on earth.
35:40It's not surprising that with so many different kinds of animals living so closely together,
35:45some extraordinary relationships have evolved.
35:52A clownfish, a small and defenseless resident of the reef.
36:00It seems to have picked a tough place to live amongst the tentacles of a sea anemone.
36:08Each tentacle is armed with paralyzing stings that can kill a fish.
36:15But the clownfish are totally immune.
36:19For this pair, the anemone is like a castle.
36:24So long as they stay surrounded by the tentacles, they're safe.
36:28And so this is where they choose to lay their eggs.
36:36After carefully selecting the site, work begins on preparing the surface.
36:52Both fish share in the labor, though it's the larger female who decides when all is
36:59ready.
37:02Lines and lines of tiny eggs are stuck to the rock and then fertilized.
37:21They're laid so close to the anemone, they will be safe.
37:27And for the next seven days, they'll receive constant care.
37:34Much of which is provided by the male.
37:39His seemingly obsessive concern for the eggs is for good reason.
37:44His position in the anemone is far from secure.
37:50The female watches his every move.
37:53He's in charge here, and if his efforts don't match up to her standards, she'll get rid
37:57of him.
38:04In line to take over are a host of immature clownfish, each waiting to move up the hierarchy.
38:22For the male, the best way to stay in the female's favor is by lavishing care on the
38:27eggs.
38:31So he focuses all his efforts on keeping them clean and healthy.
38:40The eggs grow rapidly, and soon their tiny beating hearts are visible.
38:46It seems he's done a good job.
39:01Clownfish can hide away within an anemone.
39:06But most fish don't have this option.
39:10For some, the only way of avoiding danger is by hiding amongst their own kind.
39:22In shoals.
39:35Packed close together, no one anchovy stands out.
39:42By sensing and reacting to the movements of their immediate neighbors, thousands can move
39:47as one.
39:56For a predator, picking out an individual becomes nearly impossible.
40:18The shoal's unity is its strength.
40:47Yet each fish is acting from selfish motives.
40:54Moving together, the fish confuse the sea lions so much that they leave to look elsewhere
41:03for a smaller, less tricky target.
41:07The sheer size of the shoal defeated the sea lions, but there are fish that can overcome
41:13such strategies.
41:16Off the coast of South Africa, this huge shoal of sardines is shadowed by a ragged-toothed
41:23shark.
41:30Other sharks join the menacing escort.
41:37The shoal has been driven into the shallows by a cold ocean current, and this gives the
41:45sharks an opportunity.
41:51Hundreds have moved into position.
41:58Sharks have a special sense.
42:00They can detect the electrical signals their prey gives off when it moves.
42:10It's a sixth sense that can give them an edge.
42:17But with hundreds of thousands of fish crammed into the shallows, the sharks need only rely
42:22on their speed and agility.
42:29As the first shark starts to hunt in earnest, a feeding frenzy breaks out.
42:43The shoal's defences are weakened, there isn't enough space to manoeuvre, and the sharks
42:51can gorge themselves.
42:59Despite the casualties, the shoal is so vast that the sharks have little effect on its
43:04size.
43:14Fish not only come together in great shoals for defence, but at other critical times in
43:19their lives, when they're ready to spawn.
43:24These events only occur for a few days each year.
43:35Snapper are normally solitary, but they've travelled here from hundreds of miles away
43:39to gather off the coast of Belize.
43:46Along this one reef, kubera, dog and mutton snapper form huge shoals.
44:00Sixty metres down, there is an eerie coolness to the scene.
44:06But things are about to hot up.
44:17It's the evening of the full moon.
44:20The tides are just right.
44:28A great column of fish leaves the bottom.
44:33As they rise through the water, small groups break free of the shoal.
44:47Each burst is led by a female, with the males racing behind.
44:56As she sheds her eggs, they add their sperm to the mix.
45:15By synchronising the time when they gather together, the maximum numbers of fish can
45:20join in this mass spawning.
45:27Millions of fertilised eggs are released, cast into the ocean currents, and straight
45:45into a dangerous world.
45:54Whale sharks, the largest fish on earth.
46:07Shark might weigh ten tons, yet they feed on the tiniest creatures, including snapper
46:14eggs.
46:27Life is being created, sustained and destroyed simultaneously in one huge event.
46:36The struggle for life, encapsulated into a single moment.
46:46The oceans are perilous places to live, yet fish have developed the most extraordinary
46:51means for survival.
46:56Their astounding diversity, the product of millions of years of evolution, has enabled
47:02them to triumph.
47:07Dominating the one habitat that we have so far, failed to make our own.
47:26Filming underwater raised all sorts of problems for the life team.
47:47Not least of which was that they were only able to experience the underwater world for
47:52as long as the air on their backs or in their lungs held out.
47:57But over three years, the team were lucky enough to capture on film some extraordinary
48:02moments in the lives of fish.
48:18The waters off the Yucatan Peninsula in Mexico are a rich hunting ground for sailfish.
48:31Cameraman Rick Rosenthal has teamed up with sport fishing captain Anthony Mandillo to
48:36try and film the hunting behavior of these amazing animals.
48:43When birds lead them to the sailfish, getting to the bait balls and into the water quickly
48:50is key before the feast is consumed.
49:12It's all very well telling Rick to hurry, but these fish are capable of swimming at
49:17over 60 miles an hour.
49:21But keeping up with them is hard enough.
49:42Getting right in amongst the action is vital, but Rick has to try to avoid becoming part
49:47of it.
49:50Whales nearly one meter long, scything through the water at breakneck speed, are guaranteed
49:56to get the heart racing.
50:02But Rick holds his nerve as the sailfish pick off sardine after sardine right in front of
50:20him.
50:24Almost as soon as it started, it was all over.
50:29I had a wild seashow out there today, really wild, must have been 50 sailfish or 49, but
50:41very aggressive fish, very hungry, everybody on the move, and I had to just keep kicking
50:46and kicking and kicking and kicking and kicking and kicking and keeping the action.
50:51After a while the sardine patch was eaten up to just a little sliver, and then it was
50:56over.
50:58Nearly 2,000 miles away on the other side of the Caribbean, another crew is taking a
51:03slightly different approach.
51:05They are trying to film flying fish.
51:11The team sets out at dawn on the Hog Snapper, a commercial fishing boat.
51:17Conditions are in stark contrast to the gleaming sport fishing boat in Mexico.
51:23It's Doug, he's ready for action, look.
51:34They are hoping to use the local fishermen's expertise to put them in the right place at
51:39the right time.
51:40Yeah, yeah, roger that, yeah, roger that.
51:43You catching this food?
51:45You catching dinner, lunch and breakfast, you know?
51:49Roger.
51:50It's not a big boat, and the crew's bedroom has now become the kitchen.
51:54We are having fried bacon, fried egg this morning.
51:57Fried bacon, fried eggs.
52:01I'm the trainee chef, and I don't, so I don't get to wear the white wellies.
52:11Rather than racing around the ocean chasing the action, the flying fish team have to sit
52:16it out and wait for the fish to come to them.
52:21Flying fish will spawn onto debris in the water, and the team tie onto a floating palm
52:27frond to try and make sure they're close by in case the action begins.
52:32And sure enough, they don't have long to wait.
52:37I'll take off from behind.
52:48Thousands of fish have massed below the surface, all intent on reaching the frond.
53:01And the frond is not the only thing that they're trying to lay their eggs on.
53:06The weight of the eggs sinks the palm frond and puts an end to the spawning and to the
53:35crew's filming.
53:49At moments like that we did a job where everything was right.
53:54The light was right, flew on, the four tons of flying fish all going mental.
54:01Thanks Barry.
54:02You're welcome.
54:04But now the fish's attention has turned to something bigger.
54:07They're spawning directly onto the boat.
54:11Barry is worried as he drags up a huge sheet of eggs.
54:15I clean this off like five minutes ago, right?
54:21Right now the problem is there are too many flying fish around us.
54:26If we go through the night with the lights on and stuff, more and more and more will
54:31What they're doing here is they're actually laying on the boat now.
54:34So the boat has become their object and that is not good.
54:37So basically you're worried that if we just stay on this drift we're going to sink the boat?
54:42Five hours from now that will be 3,000 pounds in the back here.
54:47They will sink the boat.
54:49OK, so we've got to leave this thing.
54:51Yeah, we can't stay here.
54:53Just five minutes of spawning has produced this.
54:57The team have no option but to move on.
55:02The next day the search for flying fish begins all over again.
55:06This time the team want to film the fish doing what they're famous for.
55:11We've got some lovely shots of them spawning but now the really hard bit of trying to get them flying.
55:16It's going to be a good challenge.
55:21The fish are around but they're all too far off to film.
55:28The action is impressive this morning.
55:31Unpredictable but impressive but it's distant and it's not happening next to the boat today.
55:36They're either being chased off by something or they're just not interested.
55:39Look, look, look!
55:41Hello!
55:43Ay yi yi!
55:46The next day the crew decides to try a different approach.
55:52All right, let's go!
55:58Now they're just where they need to be but it puts them directly in the firing line.
56:03Ha ha ha! I guess that's what!
56:14Despite being bombarded, they're still on the move.
56:19Despite being bombarded, their strategy is paying off.
56:23That was amazing. We spent a long time in that wee boat today, thanks.
56:28The last two hours were just off the scale, we were just getting shot after shot.
56:33Can't wait to watch in the big monitor, that felt really good.
56:39And Doug is right. It worked.
56:43Flying fish taking to the air and flying.
56:48Slowed down 40 times.
57:12By working with people more used to catching fish than filming them,
57:16the life team have been able to gain a unique insight into the hidden world of fish.