over half of all animals in the open ocean drift in currents jellyfish cross entire oceans feeding on whatever happens to tangle with their tentacles some can grow to a meter even 2 m across and when by Lucky chance they encounter a patch of sea rich in Plankton their numbers explode [Music] [Music] it's such a successful strategy the jellies are one one of the most common life forms on the planet but among the jellies and looking somewhat like them is a rather more complex and Sinister creature the Portuguese man of war it floats with the help
of a gas filled bladder topped by a vertical membrane with that serving as a sail it maintains a steady course through the waves [Music] [Music] long threads trail behind it some as much as 30 m [Music] long each is armed with many thousands of stinging cells a single tentacle could kill a fish or in rare cases a human but among its lethal tentacles LS a Mana War fish that feeds by nibbling them once this fish has some resistance to the stings it must still be extremely careful most other fish are not so [Music] [Applause] [Music]
lucky a tentacle has caught this one and reels it in it's already paralyzed specialized muscular tentacles transfer the victim to others that digest the catch liquefying it with powerful chemicals [Applause] eventually all that is left is a scaly husk this voracious man of war May collect over a 100 small fish in a day [Music] [Music] the struggle to survive in our green Seas can have far reaching consequences once a year one particular particular Meadow in Australia is transformed around the first full moon of winter an army materializes spider crabs for the past year they've been
feeding in deeper waters now they march across the seagrass plains [Music] hundreds of thousands of [Music] them they clamber over one another creating great Mounds [Music] nearly 100 m long they're not seeking mates neither are they laying eggs they have come here in order to grow like all crabs their bodies are enclosed in a hard unexpandable shell so to grow they have to break out of it and that allows the soft one that has developed beneath to expand it will take days for the new shell to Haren its legs are so limp that they won't
work properly the crab is unprotected and in great Danger a smooth Stingray it's huge about 4 M long it wants a soft freshly melted crab that will be easier to eat the crabs try to stick together but now disturbed by the ray they're scattering a newly molded crab is too weak to keep up with the crowd the safest place is right in the middle of the pile that is why they have all assembled here there is safety in numbers but the vast majority of the crabs Escape and within the next few days they will be
ready to return to the depths and resume their lonely wanderings in search of food this is no graveyard but the Triumph of 100,000 crabs successfully molted a Sally Lightfoot crab one of thousands of shore crabs just waiting for their moment every day they gather on the tropical shores of [Music] Brazil waiting for the tide to go out [Music] which exposes their feeding grounds seaweed covered rocks 100 m from the shore getting there is a race against the tide they leap from rock to [Music] [Music] rock these crabs seem to be afraid of the water and
for good reason the Moray eel the chain Mor is a specialist crab Hunter its blunt teeth can easily grip and crush a crab's [Music] shell it's the crabb's deadliest [Music] enemy but the crabs feeding grounds are still a long way off they must Press On [Music] halfway but the enemy has other [Music] ideas crossing the land to reset the ambush to feed the crabs must keep going but nowhere is safe an octopus also a crab killer the crabs make a dash for it made [Music] it risking life and limb to graze on these seaweed [Music]
pastures but in 2 hours time when the tide starts to turn they will have to run the gauntlet all over [Music] again in a far corner of Southeast Asia lies the Cor Coral triangle a cluster of the richest coral reefs in the [Music] world undersea cities crammed full of life as in any crowded Metropolis there is fierce rivalry for space for food and for a partner but the reef is also a Place full of opportunity [Music] a cuttlefish it specializes in hunting crabs [Music] but a large crab is a dangerous Quarry it has powerful claws
the Cuttlefish however has a remarkable Talent its skin contains millions of pigment cells with which it can create everchanging colors and [Music] patterns and that apparently hypnotizes the crab [Music] a cuttlefish may be clever but a shark is bigger and it eats cuttlefish time to disappear [Music] [Music] back to the hunt a new Target but the same mesmerizing technique [Music] for those that manage to establish themselves in these bustling undersea cities there can be great rewards during the dry season over half a million turns crowed onto this remote ATL in the Indian Ocean their chicks
are still in their dark juvenile plumage they vary in [Music] age whilst the more advanced chicks take to the air [Music] others aren't quite ready [Music] yet those just starting to learn to fly use the shallow Lagoon that occupies the center of the at all as their training ground it's difficult for some of them to stay a loft for long [Applause] [Music] giant treales usually they are solitary Hunters but about 50 of them have come here from neighboring reefs attracted by this abundance of potential prey [Applause] the fledglings stay out of the water if they
can they even drink on the wing [Music] if the chali to catch one now they have to up their [Music] game so there is a fish here that amazingly has a brain capable of calculating the air speed altitude and trajectory of a bird the time comes when every fledgling has to take to the air and collect food for [Music] itself their parents lead them to the training grounds [Music] a [Music] [Music] [Music] [Music] if they are to survive they must learn [Music] quickly after a month of practicing over the Lagoon the youngsters start to leave
and take their chances out over the Open Sea out here on the sand Flats there is safe accommodation for some a family of Saddle black clown fish have found an excellent home the tentacles of this carpet nemon can kill but the clown fish are immune to the [Music] poison so they can shelter from [Music] danger in return the fish keep the anemon clean of [Music] debris as with all clownfish the family is ruled by a big female her white face marks her out as the boss the Domin of maale has to prove his worth so
he works tirelessly removing debris and generally keeping on top of the housework [Music] his greatest challenge is to find a safe place where the boss can lay her eggs but there's nothing solid here for the female to lay them on a nearby shell could be the solution if only he can move it to the protection of the anemon [Music] too heavy besides it has a mind of its own hermit crab but out here twice a day the anemon is swept by tidal currents and they bring in new opportunities an old plastic bottle perhaps this will
do not heavy enough [Music] a coconut [Music] shell it looks just right but it's a long way from home [Music] and he can't move it by [Music] himself so the pair now work together [Music] [Music] on [Music] a little adjustment to the anemon tentacles in order to clear a space for it and the shell is tucked [Music] in the female lays a safe Nursery at last [Music] he has proved himself worthy to Father her young and he fertilizes [Music] them now he will meticulously tend the eggs [Music] keeping them clean and healthy until they hatch
in 10 days [Music] [Music] time the blue shark it travels over 8,000 km a year riding on the currents supported by its broad wing-shaped fins this one may not have eaten for 2 months but the currents can carry pring traces of fatty oils from many kilometers away and will lead it to its next [Music] meal after days of travel the smell of food gets stronger [Music] a dead whale recently struck by a ship this could be a real Feast but the blue shark must be cautious great white sharks 10 times heavier than a blue a
highly possessive around a whale carcass great whites are eager to feed on energy rich whale blubber which we now know forms a major part of their diet [Music] once the great white has had its fill smaller sharks like the blue shark tackle what's left of a carcass as the oils from this dead whale spread more widely more and more blue sharks appear [Music] within days the carcass will be stripped of its blubber then no longer longer kept buoyant by its oil it will sink Into the Depths below the blue with its reserves of fat replenished
can now survive for another 2 months without eating but most of the creatures come together for a very different reason to breed the giant cuttlefish the largest of all [Music] cuttlefish they live for just one or two years now as the Australian summer draws to an end they have one last act complete to find a mate but there are over 100,000 males competing for the arriving females in this one Bay among them a giant a true Goliath he probably weighs about 10 kilos bands of color sweep across his skin that's how cuttlefish communicate this smaller
male couldn't possibly take him [Music] on beside Goliath and under his protection a female who has just mated with him but other Rivals are still interested it seems a small male wouldn't stand a chance the female is now displaying a white stripe along her side nearest Goliath it's a clear signal that she no longer wants to mate with him [Music] it's all the encouragement that the little male [Music] needs he's going to have to use trickery [Music] he tones down his colors and Tucks in his arms he's just the right size to mimic a female
[Music] Goliath is deceived the small male now displays a white stripe just like the real female to deter his advances he slips beside her and they [Music] meet by meting with multiple partners the female ensures the greatest genetic diversity for her young the sneaky male leaves his final Act [Music] complete so even among giant cuttlefish it seems it's not all about size in the underwater forests of Northern Japan the residents of this sunken wreck are waiting for the summer temperatures to reach 16° [Music] cus that for some is the time for mating [Music] a kind
of giant Rass called a cobod die this is a [Music] male and in female terms he's particularly handsome [Music] he's a meter long and weighs 15 [Music] kilos much larger than the dimin [Music] female and he is ready to breed he attempts to mate with her and with any of the other dozen or so females that live in his territory whenever he gets the [Music] chance but females from around 10 years old take little notice of his advances [Music] [Music] this is because when any large female reaches a critical body size she can begin a
dramatic transformation over just a few months particular enzymes inside her body cease to work and male hormones start to circulate as time passes her head expands and her chin gets longer a she has changed into a he and with this comes a change in temperament the old male who ruled all the females here is challenged to a face off the more bulbous the head the more it intimidates an opponent [Music] [Music] the territory has a new ruler only the largest females transform themselves in this way but the change enables them to have more mates so
they will have many more offspring carrying their jeans [Music] but a new male can't afford to be complacent inside the body of every codai female there is a new maale in waiting and wave power creates towering fortresses like these cliffs in the Arctic home to tens of thousands of breeding seabirds the faces of the cliffs are accessible only from the air and have plenty of nooks and crannies for those that can get there but to feed seabirds must still Master the ocean World Beyond a puffin he's a fisherman and a father he has a mate
for [Music] [Applause] life both share the burden of raising their weak old chick their puffling who needs five square meals a day the parents alternate fishing [Music] trips it's Dad's turn [Music] when fish stocks are low puffins must fly as much as 50 km out to sea to reach the good fishing grounds [Music] once there they plunge into another world good fishing spots are hard to come by and they have company gilot like the Puffin their wings are short and good for diving puffins can hold their breath for over a minute and dive as deep
as 40 m a catch but it's a long way home after an exhausting round trip of almost 100 km this puffins nearly made it but there are pirates on this Coast Arctic skewers [Music] all around returning parents are being robbed [Music] the skewers long rback Wings make them faster and more maneuverable [Music] [Music] puffins must choose their moment wisely [Music] a near [Music] Miss the last desperate burst of speed and it's made it [Music] [Music] safely home after a 3-hour round [Music] trip where his patient partner is waiting [Music] [Music] [Applause] today their puffling will
[Music] eat but where fish numbers are in Decline many puffins Now find it hard to get enough food for their chicks in the changing Seas of today it can be even harder to be a successful Puffin parent [Music] a kilometer from the surface beyond the reach of the Sun a giant black void larger than all the rest of the world's habitats combined there's life here but not as we know it alien-like creatures produce dazzling displays of light nearly all animals need to attract mates and repel Predators this language of light is so widespread here that
these signals are probably the commonest form of communication on the entire planet and yet we still know little about them [Music] [Music] Hunters illuminate themselves and by doing so attract inquisitive prey [Music] this is fang tooth it has the largest teeth for its size of any fish there are precious sensors all over its head and body which can detect anything moving in the surrounding water [Music] it's the midnight Zone's most fucious fish but prey used light as a distraction a decoy of luminous ink down here in this blackness creatures live beyond the normal rules of
time siphonophores are virtually Eternal they repeatedly clone themselves some eventually growing longer than a blue whale down here it snows continuous clouds of organic debris drifts slowly down from [Music] above this is food and a whole variety of filter feeders depend on it [Music] jellyfish and delicate sea [Music] cucumbers the 1% of marine snow they miss eventually settles on the sea floor [Music] over millions of years it forms a layer of mud up to a kilometer thick it's an empty plane that covers half the surface of our planet [Music] the Deep seab bed May at
first appear lifeless but it's home to a unique cast of mud [Music] dwellers the sea toad it is an ambush Predator with an enormous mouth and infinite [Music] patience this fish has been living for so long here that its fins have changed into something more [Music] useful feet [Music] they help it shuffle about on the sea [Music] [Music] Flor the flapjack octopus it hovers just above the surface of the mud as it delicately sifts through it searching for worms but it can jet away at the first sign of danger [Music] in the Gulf of Mexico
these eruptions also release a super salty liquid Brian [Music] it's heavier than seawat and it accumulates in great pools on the seaf floor it's difficult to make sense of the site a lake of concentrated salt water 15 M deep at the bottom of the [Applause] sea around its margin perhaps even more strangely there is a profusion of life giant muscles that can live and grow for a century or more pack tightly together dwarfing the shrimps and squat lobsters that feed around them Cutthroat eels scavengers come to the shores of the Brian Lake in search of
something edible some even Venture into the brine [Music] spending too long in it can send an into toxic [Music] shock it only hope is to rise above it [Music] [Applause] it manages to escape others are not so lucky the brine inals their bodies and the casualties of decades accumulate around the margins [Music] [Music]
