Blue Planet II: Episode Guide

Josh Wright

11 Dec 2017

Our weekly review of the brand new BBC series

16 years on from the original series that brought the majesty of marine life into our living rooms, David Attenborough and the BBC Natural History Unit are back with Blue Planet II. In production for more than four years and drawing on over 6,000 hours of footage filmed across the globe, the landmark documentary series will reveal never-before-seen animals and behaviours from the surface of the ocean to its deepest depths. In our weekly reviews we’ll be recapping each episode and showing you how Natural World Safaris can help you experience the wildlife featured on the program for yourself.

episode 1: one ocean

We begin with the welcome sight of Sir David perched at the bow of a ship, who tells us that our oceans are changing at a faster rate than ever before. Blue Planet II has come at just the right time, as showing viewers the beautiful fragility of these ecosystems on a worldwide platform is the first step towards engaging everyone in conservation.

The first scene that takes place beneath the waves sees a family of bottlenose dolphins rubbing themselves against the fronds of a Gorgonian coral, a species which is thought to possess anti-microbial and anti-inflammatory properties. The adult dolphins’ ability to introduce their young calves to this peculiar form of underwater skincare points to the animals’ well-documented intelligence, as does their fondness for surfing and playing with one another. In fact, the bottlenose dolphin possesses the second-largest brain-to-body-weight ratio of any animal, behind only humans. To see them for yourself, the northern coastline of South Africa’s KwaZulu-Natal province – also known as the “Dolphin Coast” – offers a prime location.

Tropical coral reefs and atolls provide the setting for two more surprising examples of marine intelligence, this time from a pair of fish (which aren’t usually recognised as the smartest of species). Australia’s Great Barrier Reef is home to a tuskfish that is shown to break open clams by grasping them in its jaws and bashing them against a sturdy piece of coral, before retrieving the precious meat inside. Elsewhere, in the waters surrounding a remote atoll in the Indian Ocean, giant trevallies demonstrate the ability to calculate the airspeed, altitude and trajectory of low-flying terns, launching themselves out of the water to intercept the fledgling birds and drag them to a watery grave. If you’re looking to share the waters with a rich variety of marine life, try one of our Indian Ocean safaris or a trip to the picturesque cayes and atolls of Belize.

Described by legendary marine researcher Jacques Cousteau as “the world’s aquarium”, Mexico’s Sea of Cortez sees the meeting of two lifeforms that provides perhaps the most visually stunning spectacle of this episode. We see a gathering of mobula rays so large that it turns the waters a mottled grey from above, with individuals leaping clean out of the water and flapping their huge fins through the air. Scientists are still unsure why the rays do this. But as curious as this behaviour may be, it is their far more elegant movements underwater that caused our jaws to drop. By swimming through clouds of microscopic phytoplankton, the rays activate the tiny organisms’ bioluminescence, creating a stunning natural light show that has never before been captured on film.

In New Zealand and Norway, we see separate species of cetaceans coordinating in astonishing ways. False killer whales and bottlenose dolphins – both species of toothed whale - form super-pods up to 1000 strong, changing their usual calls in what may be an attempt at interspecies communication. Some scientists even argue that some individuals may recognise each other from previous encounters. Underneath the Northern Lights in Norway’s fjords, orcas work as a team to coordinate their herring hunts, herding the balls of fish before slapping and stunning the fish with their powerful tails. Eventually, humpback whales join the fray, taking advantage of the bounty offered by these rich polar seas and the confusion spread among the herring by their smaller killer whale cousins. Our small group safari to Norway offers you the chance to swim with these magnificent mammals yourself.

In between these cetacean gatherings we were treated to a host of adorable sea otters floating atop a giant kelp forest in Alaska, which is also home to the marvellously camouflaged sea dragon and the rather less aesthetically pleasing sea urchin and sea cucumber. The scene is not a mere digression, as it is revealed just how important these kelp forests are to our planet. The oceans’ seaweed, seagrass and phytoplankton species produce as much oxygen as all the forests and grassy plains on land.

Swimming through Japan’s coastal waters we find the kobudai, or Asian sheepshead wrasse. Astonishingly, the largest females, upon detecting the requisite change in water temperature, undergo a months-long metamorphosis that sees them change sex. Now larger, stronger and possessing a bulbous chin to intimidate other males, the kobudai is free to mate with their former female friends. This transformation – known as sequential hermaphroditism – is a phenomenon that occurs in numerous species of fish and gastropod, as well as plants.

The first episode’s final scene takes place in Svalbard, an archipelago in the Arctic Circle that is a favourite of Natural World Safaris clients. Despite its northerly position, the Gulf Stream current makes Svalbard habitable for humans as well as an array of native wildlife. Walruses and polar bears share the coastlines and ice floes, which we find are melting at an alarming rate. Climate change trends are most pronounced in the polar regions, with the extent of Arctic sea ice in the summer having been reduced by 40% over the last 30 years. For your chance to visit this imperilled yet beautiful land, our range of Svalbard safaris allow you to spot wildlife among its fjords, glaciers and mountains while in the company of expert guides, photographers and climate researchers.

Episode 2: The Deep

Our oceans can often feel like another world, but the second episode of Blue Planet II showed that their deepest depths are a truly alien environment. In “The Deep”, we descend through the so-called “twilight zone” – which extends from a depth of around 660 to 3,300 ft – down to a world where no sunlight penetrates at all. Inside the Mariana Trench, the very deepest part of the world’s oceans, the pressure is so immense that standing on the bottom would be the equivalent of having 50 jumbo jets stacked on top of you. But even here, almost seven miles from the surface, there are natural wonders aplenty. Once thought to be as devoid of life as it is light, we now know that the deep ocean contains more living organisms than anywhere else on earth.

We know less about the deep than we do about the surface of Mars, 30 million miles away. This quite astonishing fact shows just how difficult it is to explore our oceans. 12 people have walked on the moon; just three have made it to the deepest part of the Mariana Trench, almost seven miles from the surface.

After last week’s episode, which saw families of dolphin, orca and walrus living near the ocean’s surface, we witness a weird and wonderful cavalcade of bizarre creatures which at times beggars belief. We see a bioluminescent siphonophore, which is not one creature but a colony of tiny interconnected organisms that are capable of cloning themselves as they drift through the ocean, making it essentially ‘eternal’. The barreleye is a fish whose skull is filled with transparent jelly, allowing it to look straight up in order to keep track of potential prey.

Gone is the beguiling footage of a tuskfish cracking open a clam against the backdrop of a tropical coral reef. Instead we witness the decaying carcass of a sperm whale sinking to the bottom of the ocean, set upon by deep-dwelling sharks the size of great whites and a host of scavengers which feast upon the remaining remnants of flesh, before acid-secreting zombie worms burrow into the bones to extract the last shreds of sustenance available before the whale’s skeleton eventually sinks into the mile-thick layer of organic debris that makes up the seafloor.

Filmmakers would be hard-pressed to turn any of these denizens of the deep into the star of the latest animated kids’ movie. Giant spider crabs move around on their elongated limbs like macabre puppets, Humboldt squid cannibalise each other and the dead-eyed ambush predator known as a sea toad gazes up at its prey before walking around on a bizarre set of fins that have morphed into primitive “feet”.

But the same creatures that can make our skin crawl can also make our jaws drop. Not all of us will want to come face to face with a fangtooth, the fish with the largest teeth relative to its body size in the entire ocean, but simply knowing we share our planet with such extraordinary living things is enough to make us cherish our planet just a little bit more. Perhaps the most surprising discovery revealed by this episode was the sheer amount of life that congregates around hydrothermal vents. These fissures in the earth’s crust produce scolding streams of water hot enough to melt lead. Crabs covered in snow-white hairs feed on plumes of hydrogen sulphide, a gas toxic to most living things. Aside from the intense heat found here, another by-product of the volcanic activity turns out to be a rich collection of bacteria and minerals that can sustain a surprising amount and variety of life. Joining the crabs is a community of organisms including shrimp, corals, sponges, limpets and tube worms.

Our dulcet-toned narrator tells us that by looking into the ocean’s depths, we may also be looking into our past. These hydrothermal vents have been found to spontaneously produce hydrocarbons, a key component within all living things. Due to this, one theory for the origin of life itself is that it began in the deep sea in a place like this. Natural World Safaris are yet to offer any excursions to the deep ocean, but if you’re after a marine safari that doesn’t require a multi-million dollar submersible, we’ve got you covered. From swimming with alive-and-kicking sperm whales to observing penguins in Antarctica, our trips put you in the right place at the right time to experience the wildlife that calls the upper parts of our ocean home.

Episode 3: Coral Reefs

After the thoroughly alien and pitch-black world of the ocean’s depths that we visited last week, Blue Planet II’s third episode was a riot of life and colour. Coral reefs were the setting for turtle health spas, dolphin playgrounds and spectacular spawning events that were in stark contrast to the bizarre deep-sea beings that blew us away in “The Deep”. The differences between the animals across each episode helps to put into perspective the sheer size and scale of our planet’s largest habitat. Although coral reefs themselves cover less than 0.1% of the seafloor, they are home to a quarter of all known marine species. Our narrator Sir Attenborough refers to these habitats as ‘cities’ that are home to underwater ‘civilisations’, and after an hour of witnessing the density and variety of life here, these end up being rather apt analogies.

The first scene features a broadclub cuttlefish engaging in a hypnotic display to bewilder a passing crab, morphing their mantle and tentacles into different shapes and rapidly changing its colour by utilising specially pigmented cells called chromatophores. Remarkably, cuttlefish eyes are unable to perceive colour, leaving the exact mechanism behind their colour-changing ability a mystery. Next, we’re introduced to a dynamic duo whose teamwork would put Nemo and Dory to shame. Back in Blue Planet II’s opening episode, we saw pods of bottlenose dolphins and false killer whales meeting and greeting each other, but this latest example of interspecies communication almost beggars belief. Groupers and reef octopuses could hardly be more dissimilar in appearance, but by working together to flush out prey fish from within their coral hiding place, they form a mutually beneficial partnership. Octopuses’ high level of intelligence has long been a subject of study, but it is the grouper’s “headstand” that appears to initiate the predators’ collaborative manoeuvres. Just as the tool-using tuskfish and bird-hunting trevally did in Episode 1, this scene shows that perhaps we need to re-evaluate our understanding of fish brainpower.

Just four types of reptile have displayed adaptations required for a marine lifestyle: turtles, snakes, iguanas and crocodiles. The green turtle is one of the most charismatic residents of the world’s coral reefs, and it knows it: the waters around Borneo are home to the ocean’s premier turtle spa. Settling down for an early-morning pampering, the turtle is attended by blennies and surgeonfish which remove parasites, dead skin and algal growth from those hard-to-reach places. As with the grouper and octopus, this symbiotic relationship shows that the ocean is not always a dangerous place; until a larger turtle comes along and jumps the queue, of course. The reefs of the Red Sea provide an even more pleasant locale for groups of young bottlenose dolphins, who play amongst each other with discarded corals and sponges. In Episode 1, we saw the same species rubbing against a type of coral thought to possess anti-microbial and anti-inflammatory properties, and this latest footage gives added weight to the dolphins having an intimate knowledge of and connection with their habitat.

A visually stunning sequence filmed via drone granted us an aerial view of massive manta rays engaging in a “cyclone” of feeding activity, with over 50 rays creating an underwater vortex that allows the animals to more easily catch their preferred prey of plankton. Continuing the theme of teamwork running through the episode, we see saddleback clownfish eking out an existence on an outlying anemone away from the main reef, who must work together to ensure a safe and suitable location to rear their children. The smaller male must prove his worth by furnishing the female with a stable surface on which to lay her eggs. An algae-covered plastic bottle is a stark reminder of the effect that we are having on the world’s oceans, and the clownfish are unable to adapt the rubbish to their new home. But soon salvation appears in the form of a coconut shell, which the male manages to take home (after some committed nose-shoving). Even the sequence involving the terrifying metre-long Bobbit worm, which ambushes unsuspecting fish and drags them into its lair underneath the seafloor using razor-sharp pincers, was the scene of some heartwarming underwater teamwork. During daylight hours, some fish take it upon themselves to blow away sand from the top of the Bobbitt worm’s burrow, sabotaging its camouflage and allowing their friends to avoid the deathtrap. They just need to make sure not to get too close…

The episode’s final two scenes feature two underwater spawning displays that were jaw-dropping for their alternating savagery and beauty. Near a French Polynesian atoll, thousands of groupers gather at the edge of a reef to engage in mass reproduction, but they’re not being given any privacy. Hundreds of reef sharks descend upon the fish, the groupers’ flesh and blood mixing with their eggs and sperm as the prey sacrifice themselves in an effort to fertilise. Elsewhere, in a stunning example of synchronicity, a vast swathe of individual corals all release their gametes into the water at the same time, creating a beautiful underwater snowstorm that will hopefully ensure the survival of the coral species for years to come, as they drift away to settle in whichever portion of the seafloor that the currents take them. To experience these astonishing habitats for yourself, Natural World Safaris offers a range of marine holidays to some of the most beautiful marine destinations in the world, including the azure waters of the Indian Ocean and the coral reefs of St. Helena, Borneo and the Kenyan coast.

Episode 4: Big Blue

Venturing far away from the niche habitats seen in “The Deep” and “Coral Reefs”, the latest episode of Blue Planet II showed us the creatures inhabiting the world’s greatest wilderness: the open ocean. It may seem a wonder how any animal can find food and mates here, such is the vast and seemingly barren expanse of water that occupies the earth’s surface between its landmasses. But this habitat – essentially a marine desert – is home to some of the largest creatures on earth and some truly spectacular convergences of wildlife that can’t be seen anywhere else.

A sperm whale featured heavily in the second episode of Blue Planet II, its carcass providing food for a host of different deep-sea creatures as it sank to the bottom of the ocean several miles below the surface. But this week we were able to see what the largest toothed predator in the world is really capable of. These whales have the largest brain of any animal, and in some extraordinary footage we saw them using a complex vocalisation system to both find prey and communicate with each other. Although incapable of producing the “songs” synonymous with other species like the humpback whale, sperm whales utilise clicking to locate their prey, sounds which bounce off their quarry and travel back through the whale’s spermaceti, letting the whale know how far away different objects are. Sound travels four times faster in water than in air, so this ingenious hunting mechanism – also found in dolphins and porpoises - is likely a result of cetacean ancestors making up for the decreased effectiveness of sight and smell underwater. This focussed transmission and reception of sonar signals is also thought to coordinate sperm whale families in everything from childcare to hunting. Our Dominican safari - departing in February 2018 - offers you the chance to swim alongside these fascinating creatures.

The series’ contribution to science continued with this episode’s exploration of the so-called “lost years”, the name given to the expanse of time between a sea turtle’s birth and its return to coastal waters a number of years later. Until then, juvenile turtles are known to lead a pelagic lifestyle (that is, remaining in the open ocean). But how they survive and where exactly they go to grow and feed has remained a mystery for decades. Scientists have contended with the difficulty of tracking hatchlings due to electronic tags either being too heavy or interfering with the turtles’ growth. But the fantastic footage in “Big Blue” reveals that some young turtles don’t just drift aimlessly, but instead use pieces of floating debris like logs or seaweed as mobile homes, where their food sources include molluscs, crustaceans, jellyfish and fish eggs. To witness the magnificent wildlife spectacle that is turtle nesting, Tortuguero National Park in Costa Rica offers the perfect place for sightings.

We were also treated to another innovative sequence which brought us closer to unravelling another marine mystery. Despite their immense size – the largest recorded specimen was 41.5 ft long – the location of whale sharks’ birthing grounds has been unknown to science since the discovery of the species. But after witnessing the pregnant females embarking on an epic journey across the Pacific Ocean to the Galapagos Islands, it is now thought that this may be where whale shark pups are born. The Galapagos Whale Shark Project has reported that the majority of whale sharks sighted in the Galapagos Marine Reserve are large, sexually mature females, over 90% of which appear to be pregnant. Scientists are still unsure of how and where whale sharks breed, but the work done by the Blue Planet II team has proved immensely valuable to ongoing research (and the footage wasn’t half bad either). Seasoned swimmers can swim with these gentle giants on our safari to the beautiful and remote island of St Helena, in the Atlantic Ocean.

By contrast, the phenomenon of “boiling seas” had been known to sailors for centuries, but had never before been captured on film. This isn’t evidence of the kind of hydrothermal activity we saw in Episode 2, however. The reality behind this myth is that it is in fact a feeding frenzy, an astonishing density of biomass converging on a hapless shoal of lanternfish who are preyed upon by spinner dolphins, tuna, sailfish and even mobula rays, previously thought to exist solely on plankton. The Blue Planet II videographers have thus provided the first evidence that these graceful creatures include fish in their diet. Once again, in addition to producing some jaw-dropping footage, the BBC have contributed to our understanding of the remarkable breadth of marine life that is often more difficult – sometimes even impossible - to observe when compared to terrestrial life.

The episode ends with a grim reminder of the effect humanity is having on the marine world, with an estimated eight million tonnes of plastic dumped into the oceans every year. Even creatures living at the seas’ deepest point have been found with manmade materials in their stomachs. In the Atlantic, we see a recently deceased pilot whale calf whose death may have been caused by its mother’s poisoned milk. Tragically, when plastic and other pollutants enter the food chain, they end up concentrated to potentially lethal levels when consumed by animals near the top of the chain, like pilot whales. Studies suggest that there are around five trillion pieces of microplastic in the ocean, and humans consume around 11,000 pieces per year as a direct result of eating seafood. If trends continue, this number will rise to 780,000 by the end of the century. We must not allow ourselves to forget the global crisis that every living thing faces when the wonders of this documentary series are off our screens.

Episode 5: Green Seas

This week’s episode of Blue Planet II introduced us to a new marine habitat, one which mirrors the prairies and forests we see on land. First we pass through forests of kelp that sustain a diverse range of life. These seaweeds are actually a form of algae, and certain species can grow up to 260 ft tall. Next we inspect vast stretches of sea grass, the ocean’s only flowering plant, which serve as underwater meadows frequented by both predator and prey. Mangrove forests, which straddle the boundary between land and sea, are another environment which sea creatures have made their own. And in the episode’s final scene, we see the great contribution that kelps’ much, much smaller cousin - microscopic algae – can bring to the oceans.

Back in Episode 3, “Coral Reefs”, we were shown one example of octopuses’ considerable intelligence, with one species cooperating with a grouper in order to flush out prey from their hiding places. Here in a kelp forest off the tip of Africa, the common octopus has developed some ingenious tactics to ensure this predator doesn’t end up as prey. Octopuses have no bones and a body made up mostly of soft tissue, allowing them to squeeze into impossibly small places. But even then, its nemesis here – the pyjama shark – is able to root out the cephalopod and attempt to make a killing bite.

This isn’t the end of the octopus, however. Locked in a lethal embrace, it pushes its arms into the gills of the shark, blocking its airways. The shark has no option but to let the octopus go. But even then, trapped in the open, the octopus has one last trick up its sleeve to avoid becoming dinner. Incredibly, it covers its body in the discarded shells that line the seabed, creating makeshift armour-plating that protects its vulnerable body from the shark’s sharp teeth. This remarkable scene provides yet more evidence that the octopus is one of the most intelligent animals in the ocean.

Along the Pacific coast of North America, the residents of another kelp forest demonstrate the delicate balance struck within an ecosystem. Garibaldi fish must contend with invaders to their patch of seaweed territory: spiny urchins. These bizarre spiked creatures are the aphids of the marine world, feeding on underwater greenery like the type protected by this plucky orange fish. But until around a century ago, it wasn’t the Garibaldi who kept the urchins in check, but sea otters, who once numbered in the hundreds of thousands. Hunted relentlessly for their fur starting in the late 1800s, the population crashed, resulting in unchecked urchin devastation to kelp forests. But thanks to the efforts of conservationists and an international hunting ban, the species has rebounded, and is starting to bring this enchanting ecosystem back into balance.

Sea grasses are the backdrop for three more scenes of underwater drama. First a tiger shark stalks a green turtle, which grazes on the seabed much like a tortoise does on the land. But unlike the previous shark scene, this one doesn’t end in a battle. Instead, we are again taught about the benefit to this ecosystem brought about by the occupant of the top of the food chain preying on something at the lower end. By pursuing the turtle across the seabed, the shark effectively shepherds the turtle around the sea grass meadow, allowing the grass to regrow and sustain itself. This is important not just for the plant, but for the planet - a patch of sea grass is 35 times more efficient at absorbing and storing carbon than the same area of rainforest.

Much like prairies on land, sea grass meadows attract huge gatherings of animals. Writhing hordes of spider crabs gather off the coast of Australia in such numbers that in some places they form towering piles, one on top of the other. They are here not to breed or mate, but to shed their old shells. The reason they do this together soon becomes apparent – their new shells take days to harden, leaving the crabs' bodies soft, vulnerable and unable to move properly. Before long, 13 ft-long stingrays swoop down to take advantage of the banquet. Further up the coast, the largest gathering of cuttlefish in the world takes place, and we’re treated to another example of these animals’ colour-changing abilities which we saw in Episode 3. Here a small male imitates the markings of a female to trick a larger male into letting down his guard, allowing the new suitor to make off with the old one's bride.

Mangrove forests are made up of trees and shrubs that grow in coastal or brackish water, and their labyrinthine network of underwater roots have been adapted into the perfect habitat for a number of marine species. They have been particularly co-opted as nurseries by spawning fish, as juveniles are able to find much more shelter here than in other parts of the coast or the open ocean. Still, these small, defenceless fish make easy prey for those able to navigate the mangroves. At over 15” long, the zebra mantis shrimp is the largest mantis shrimp in the world, but manages to cover itself in sand – not unlike the bobbit worm in Episode 3 – and pounce on its unsuspecting quarry. Although some species are thought to mate for life, this mantis shrimp is seen leaving its partner of 20 years in favour of a larger female. With the male gone, the dejected female and her offspring are likely to starve.

In the episode’s final scene, temporary blooms of microscopic algae attract billions of plankton-feeding fish, sparking a feeding frenzy that attracts thousands of larger predators, including dolphins, sea lions and even humpback whales. “Green Seas” shined a light on a series of lesser-known but nonetheless fascinating ocean ecosystems, showing us that there is more to our blue planet than the “big blue” of last week’s episode. Our Bears, Waterways and Wilderness Safari to Alaska and Canada takes you on a 16-day journey along the North American coast where giant kelp forests thrive, giving you a chance to see the seals, sea lions and sea otters which form part of this amazing marine ecosystem.

Episode 6: Coasts

Diving to the deepest depths of the oceans in a specially built submersible and witnessing feeding frenzies hundreds of miles from land are experiences that only some of us will ever have the good fortune to live through, but the penultimate episode of Blue Planet II brought the focus to a habitat that we’re all familiar with: coasts. More than half of the world’s population lives within 60km of the ocean, and two-thirds of our major cities are located next to it. This isn’t to say that the scenes we witnessed were quotidian, however. From time-lapse images of life-and-death drama in shallow rockpools to never-before-seen hunting strategies, “Coasts” revealed the extraordinary animal behaviours that can occur where land meets sea.

The first opportunists we see making the most of this transitional environment are sea lions in the Galápagos Islands. Operating off a tip from a local fisherman, the Blue Planet II team travelled to the remote archipelago to capture the marine mammals effectively herding fish into shallow coves, working together to cut off the fishes’ escape. These weren’t just any fish, however: these were yellowfin tuna, huge, fast and weighing around 60kg. The tuna are able to avoid being caught by sea lions in the open water due to their superior speed – mature individuals travel at an average speed of 1.2 metres per second. But when herded into the coves and faced with hungry mouths on one side and dry land on the other, the fish don’t stand a chance.

Throughout this series we have seen ocean-dwellers demonstrate new behaviours that cause us to rethink how intelligent certain species are. Sequence director Rachel Butler was sceptical about the tale, but sure enough, the sea lions worked in coordinated teams to kill their prey, each member taking on a specific role to ensure the tuna were herded into specific coves and were blocked from finding their way out. It’s clear the sea lions have both brains and brawn though, as the episode’s behind-the-scenes section, “Into the Blue”, showed the sea lions having to fight for their catch with ravenous Galápagos sharks!

Next, time-lapse footage taken in a rockpool along British Columbia’s coast revealed a surprisingly active world with just as much predator-prey drama as one may find on the African savannah, although taking place (at least to our eyes) in slow motion. The effect is similar to that used in The Private Life of Plants, a 1995 BBC series which used the process to show the plant kingdom in a different light. But despite the appearance of some of the creatures in this rockpool, they’re animals, not plants. Starfish crawl ominously across their underwater environment on countless tube-like feet which project from the underside of each arm, in search of prey like limpets. But these aquatic snails have a number of defences, including the parasitic scale worm which lives underneath the limpet’s shell. We also see a green sea anemone drawing a mussel into its digestive tract, pulsing bizarrely in an attempt to digest its meal. Clearly there are hidden dramas unfolding every day in environments such as this.

Just as the sea lion sequence was all about coordination, this next one was all about timing. On the coastline of Brazil, Sally Lightfoot crabs must wait until the tide goes out to uncover the route to their feeding grounds, algae-covered rocks that were submerged beneath the waves just hours before. The crustaceans demonstrate remarkable agility as they bound from rock to rock, but they’re certainly not jumping for joy. This journey is in fact a deadly gauntlet, with predators lurking in the shallows awaiting a fatal slip or misjudged leap. The chain moray eel can grow up to 18” long and is capable of launching itself out of its hiding place to drag unsuspecting crabs to a watery grave, and it can even slither along the rocks like a snake. The plucky crustaceans must also contend with another predator capable of moving across land: an octopus. Unlike the octopus-grouper partnership in Episode 3, however, there seems to be no coordination with the nearby moray, and the eight-armed hunter goes hungry this time.

We see no wholesome interspecies connection on Norway’s coast either. Atlantic puffins must fly up to 30 miles out to sea to bring back fish for their young, but even after a successful catch, they must defend their pufflings’ food from those who would relieve them of it. Arctic skuas are larger, faster, and more aerobatic than puffins, and one deftly placed talon could make the puffins’ entire journey come to naught. Half a world away, on the remote island of South Georgia in the Atlantic, another bird species faces a different challenge, but this one doesn’t involve food. Once a year, king penguins flock to this piece of land to shed each of the four layers of feathers which keep them insulated when swimming through the frigid Antarctic seas. This is referred to as a “catastrophic moult”. The month-long process requires the penguins to stay out of the water and thus starve themselves, and to make matters worse, they must find their way through a blubbery wall of hauled-out elephant seals – with aggressive males weighing up to 4 tonnes - before they can begin.

This episode also showed animals cropping up in places you wouldn’t expect. The Pacific leaping blenny is the most terrestrial fish on the planet, living in miniature caves above the tideline and literally leaping out of the way of incoming waves to avoid being sucked underwater. But despite the fact that they breathe air, they do so through their skin, meaning they must moisten themselves constantly to avoid drying out and suffocating. These tiny fish truly live on the edge – in more ways than one. In another example, we learn that the largest gathering of coastal sharks on the planet occurs in sight of first-world swimming pools and tower blocks. Every year, the warm waters off Florida’s Palm Beach attract thousands of spinner and blacktip sharks, which stop off here during their migration northwards to colder climes. That this happens right next to a U.S. town where men and women go about their daily lives (and who aren't in a state of Jaws-induced panic) is quite remarkable.

“Coasts” showed us that the natural world can serve up marine wonders even in shallow waters, and that the place where land meets sea is not a place where two habitats meet, but rather a habitat all of its own. Natural World Safaris operates trips to a number of destinations featured in this episode, including an island-hopping adventure to the Galápagos and a British Columbia safari to see humpback whales, porpoises, sea lions and orcas. Brazil offers plenty of opportunity, as does Norway – where one can actually swim with killer whales and humpbacks – while our 2018 South Georgia safari will be in the company of award-winning photographer David Yarrow.

Episode 7: Our Ocean

The focus for the final episode of Blue Planet II was not on a particular habitat or species, but instead on our relationship with our oceans. By returning to the animals featured in some of the series’ most memorable sequences, we see how humans are both endangering the marine world and working to save it.

In Episode 1, we witnessed the spectacle of a Norwegian herring hunt that attracts hundreds of humpback whales and one of the largest gatherings of orca on the planet, as well as a flotilla of fishing vessels. NWS Gemma dived with these whales on her recent trip to Norway. Here these three mammal species, although not necessarily working together, co-exist peacefully in their joint efforts to reap the sea’s bounty. But by looking behind the scenes we discover that this is only possible thanks to strict fishing regulations and the work of dedicated conservationists. Billions of herring flock to these fjords every winter, but 50 years ago the population here was almost wiped out. Although a veritable conservation success story, the close-quarters nature of the herring hunt still poses a danger to the whales that participate in it: one large orca becomes trapped in a fishing net onscreen, and only survives once the fishermen onboard their boat receive permission via radio that they are able to release the net. Thousands of miles of fishing nets and lines enter the world’s oceans every day, and bycatch is one of the biggest threats facing a host of marine animals: each year, it kills over 300,000 cetaceans, around 250,000 turtles and as many as 100 million sharks.

A plastic bottle made an unwelcome cameo back in Episode 3, when a family of saddleback clownfish tried unsuccessfully to install it in their anemone home as a makeshift nursery. But despite more than eight million tonnes of plastic ending up in our oceans every year, there is another danger facing these clownfish - one we can’t even see. Diving beneath the waves with marine biologist Steve Simpson and his sophisticated hydrophone (a microphone designed to be used underwater), our living rooms were suddenly filled with a coral reef chorus contributed to by all the residents of the reef. For the clownfish in particular, sound plays a vital role in their lives, as their chirps and cheeps are used to communicate between each other and warn of potential danger. But noise pollution isn’t just an issue on land, it seems: manmade sounds like boat engines and offshore drilling can interfere with this communication, making marine animals that rely on it vulnerable to predation.

Plastic reared its non-biodegradable head in the episode’s next scene as well. Dr Lucy Quinn of the British Antarctic Survey presented a stomach-turning selection of rubbish that had been regurgitated by albatrosses living on the remote island of South Georgia in the South Atlantic. Among the items are food packaging, clingfilm, rubber gloves, toothbrushes, bottle caps and polystyrene foam. And despite albatrosses’ inherent ability to void their stomachs in order to remove indigestible parts of their usual diet, like squid beaks, manmade refuse can still be lethal: Quinn stands over the carcass of an albatross chick, its stomach ruptured by a stray toothpick, the victim of human negligence. Even for an animal born on an island over 800 miles away from the nearest permanently inhabited piece of land – the Falklands – careless waste on the part of humans has led to death and disruption within an ecosystem.

In Trinidad, one man’s commitment to protecting the leatherback turtle has resulted in an entire community coming together to save these endangered seagoing reptiles and their eggs from poaching and predation. Over a period of around 20 years, a single beach has seen an increase from 30-40 nesting turtles a night to over 500. Through educating the local people and bringing tourism to the area, Len Peters and the rest of the team at Turtle Village Trust have brought the species back from the brink in this area. Turtles face the same kinds of threats as many other marine species, including entanglement in fishing equipment, harmful consumption of plastic and hunting for either their flesh or their eggs. Len’s story shows the impact that just one person can make to a species under threat if their passion and dedication for protecting the natural world is unwavering. A gathering of hundreds of sperm whales in the seas surrounding Sri Lanka, seen later in the episode, underscores this point when it is expanded to entire nations, as it was with the 1982 moratorium on commercial whaling.

Learning more about the animals we share our planet with is another way we can work to save them. In Episode 4, we saw how scientists took great strides in unravelling the mystery of where whale sharks give birth, and in this final episode we accompany shark biologist Jonathan Green as he embarks on this journey. The world’s largest fish – classified as endangered by the IUCN – is killed in the thousands each year by fishermen, so understanding where the sharks give birth is integral to protecting new generations. Green dives with the sharks, attaches remote cameras to them and even dives to great depths in a submersible to follow the animals as they descend so far down into the waters surrounding the Galápagos Islands that all light from the surface disappears. But despite the mother-to-be getting away from Green, he is able to see – with the help of the lights on his submersible – the environment where whale shark pups likely live out their first years, far down enough to be protected from possible predators. They will eventually grow large enough that they will have no natural predators; apart, that is, from humans.

Bleached coral reefs and calving ice shelves are dramatic visual symbols for humanity’s impact on the world’s oceans that instantly stir up guilt, grief and a nervous anxiety for the future of our planet and the living things that we share it with. But this landmark documentary series ends with a message of hope. “We are at a unique stage in our history,” says Sir David, himself a source of inspiration for generations of nature-lovers. “Never before have we had such an awareness of what we our doing to the planet, and never before have we had the power to do something about that.” Blue Planet II is already the most-watched television program in the UK this year, and by showing us both the beauty and the fragility of our oceans, the BBC Natural History Unit have taken a massive step towards engaging everyone in the vital issue of conservation.

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