0:00:38 > 0:00:39The open ocean.
0:00:41 > 0:00:45It covers more than half the surface of our planet.
0:00:45 > 0:00:49Yet, for the most part, it's a watery desert,
0:00:49 > 0:00:51empty of life.
0:00:54 > 0:00:59Hunters here spend their lives in a constant search
0:00:59 > 0:01:02for scarce and elusive prey.
0:01:16 > 0:01:20Remarkably, this seemingly barren wilderness
0:01:20 > 0:01:24is home to the largest hunter of them all...
0:01:29 > 0:01:31..the blue whale.
0:01:40 > 0:01:43Weighing 200 tonnes
0:01:43 > 0:01:45and 30 metres long,
0:01:45 > 0:01:48these are the biggest animals ever to have lived.
0:02:02 > 0:02:05Despite their immense size,
0:02:05 > 0:02:08blue whales are one of the most streamlined
0:02:08 > 0:02:11and energy-efficient of all swimmers.
0:02:22 > 0:02:25Their food is so scarce and widely spread
0:02:25 > 0:02:30that blue whales must journey across whole oceans
0:02:30 > 0:02:33just to find a single meal.
0:02:40 > 0:02:45They can travel over 100 miles a day for weeks at a time.
0:02:58 > 0:03:03The ocean's largest animal feeds on one of its smallest.
0:03:05 > 0:03:08Krill - small shrimp-like crustaceans.
0:03:16 > 0:03:20Opening its gigantic mouth takes so much effort
0:03:20 > 0:03:21that they only do so
0:03:21 > 0:03:24when the swarms of krill are rich and concentrated.
0:03:31 > 0:03:34The krill here is too scattered -
0:03:34 > 0:03:36not even worth slowing down for.
0:04:09 > 0:04:13This blue whale's lonely search for food
0:04:13 > 0:04:14must go on.
0:04:21 > 0:04:26Out here, feeding opportunities are always few and far between.
0:04:27 > 0:04:29And they never last long.
0:04:36 > 0:04:38Prey is devoured within minutes.
0:04:48 > 0:04:49When it's all over,
0:04:49 > 0:04:53the hunters must resume their endless search.
0:04:57 > 0:04:58Frigatebirds -
0:04:58 > 0:05:00the pirates of the high seas.
0:05:02 > 0:05:06Soaring effortlessly on the gentle trade winds,
0:05:06 > 0:05:09they can scan vast tracts of ocean for food.
0:05:12 > 0:05:14Frigates must be so lightweight
0:05:14 > 0:05:16that they can't afford the heavy oils
0:05:16 > 0:05:20that waterproof the plumage of other sea birds.
0:05:20 > 0:05:23So getting wet would be lethal.
0:05:24 > 0:05:29This may seem an impossible limitation for a seafaring hunter.
0:05:29 > 0:05:31But frigatebirds overcome this handicap
0:05:31 > 0:05:33with help from others.
0:05:42 > 0:05:43Dorado.
0:05:45 > 0:05:48One of the fastest and most voracious of ocean predators.
0:05:52 > 0:05:55They patrol close to the surface, searching for prey.
0:06:05 > 0:06:09Little fish try to hide amidst the undulating swell of the ocean -
0:06:09 > 0:06:11the only cover there is.
0:06:18 > 0:06:20It's a game of hide and seek
0:06:20 > 0:06:22played out amongst the waves.
0:06:26 > 0:06:28Their cover blown...
0:06:30 > 0:06:32..escape seems impossible.
0:06:41 > 0:06:44But these particular fish have a unique ability.
0:06:59 > 0:07:01They're flying fish.
0:07:23 > 0:07:26With an extra thrust from their tails,
0:07:26 > 0:07:28the flying fish get airborne once more.
0:07:37 > 0:07:38With a good wind,
0:07:38 > 0:07:40they can glide for hundreds of metres.
0:07:58 > 0:08:01But this is just what the frigatebirds
0:08:01 > 0:08:02have been waiting for.
0:08:06 > 0:08:08When frigates join the hunt,
0:08:08 > 0:08:12the flying fish are literally caught between the devil...
0:08:14 > 0:08:16..and the deep blue sea.
0:08:36 > 0:08:38If the flying fish get too much lift
0:08:38 > 0:08:41they become easy prey for the frigates.
0:08:56 > 0:08:59If they dive to evade attack from above...
0:09:03 > 0:09:06..they could fall into the mouths of the dorado.
0:09:48 > 0:09:49With the help of the dorado,
0:09:49 > 0:09:54the wily frigatebird has become a flying fish specialist...
0:09:55 > 0:09:58..and without getting a single feather wet.
0:10:04 > 0:10:07Not all open-ocean hunters are able to travel
0:10:07 > 0:10:10in search of their food.
0:10:10 > 0:10:15Some have no choice but wait for a meal to come to them.
0:10:19 > 0:10:24A mat of sargassum weed drifts in the middle of the Atlantic.
0:10:30 > 0:10:34Sargassum is the only seaweed to live entirely at the surface.
0:10:36 > 0:10:38It never attaches to the sea floor.
0:10:42 > 0:10:45This floating tangle of fronds
0:10:45 > 0:10:49is home to a surprising open-ocean predator -
0:10:49 > 0:10:51the sargassum fish.
0:10:55 > 0:10:58Every part of his body mimics the weed.
0:11:01 > 0:11:04His fins are more suited to walking than swimming.
0:11:06 > 0:11:09In fact, he can barely swim at all.
0:11:11 > 0:11:16He will spend his entire life marooned on this weedy raft.
0:11:24 > 0:11:28This sargassum fish must lie in wait
0:11:28 > 0:11:31for those seeking shelter amongst the weed.
0:11:44 > 0:11:47Unfortunately his mat is empty for now.
0:11:49 > 0:11:52But at least he's not wasting valuable energy
0:11:52 > 0:11:53searching for food.
0:12:00 > 0:12:02In the featureless ocean,
0:12:02 > 0:12:06these mats are much-sought-after sanctuary for juvenile fish.
0:12:23 > 0:12:25At last -
0:12:25 > 0:12:29his first opportunity for weeks.
0:12:36 > 0:12:37He must get closer.
0:12:38 > 0:12:43He can only strike when he's within a few centimetres of his prey.
0:12:53 > 0:12:56Trusting his perfect camouflage,
0:12:56 > 0:12:58he hides in the weed.
0:13:04 > 0:13:05Patience.
0:13:10 > 0:13:12Still not close enough.
0:13:24 > 0:13:27Hunger is clearly getting the better of him.
0:13:40 > 0:13:42Surely this time.
0:13:46 > 0:13:47Blown it.
0:13:49 > 0:13:53It may be weeks before he gets another chance.
0:14:08 > 0:14:10The open ocean is so vast
0:14:10 > 0:14:13that some hunters can only find enough prey
0:14:13 > 0:14:15by searching as a team.
0:14:30 > 0:14:34Dolphins live in highly sophisticated social groups.
0:14:43 > 0:14:44Working together,
0:14:44 > 0:14:47they can cover a huge area of ocean.
0:14:52 > 0:14:54These are spinner dolphins.
0:14:57 > 0:15:00Why they make these twisting leaps is still debatable.
0:15:00 > 0:15:03Perhaps it's a form of communication...
0:15:07 > 0:15:09..or perhaps it's just fun.
0:15:11 > 0:15:14Small groups sometimes come together,
0:15:14 > 0:15:17forming superpods 5,000 strong.
0:15:24 > 0:15:26And these are on the hunt.
0:15:34 > 0:15:36SONAR CLICKS
0:15:36 > 0:15:39Spinners are the most vocal of all the dolphins.
0:15:39 > 0:15:41CLICKING AND CRACKLING
0:15:42 > 0:15:47They use echolocation, a kind of sonar, to find their prey.
0:15:48 > 0:15:52Each hunter sends out a series of clicks
0:15:52 > 0:15:55and then listens for returning echoes...
0:15:58 > 0:16:01..allowing them to scan for distant prey,
0:16:01 > 0:16:02hundreds of metres away.
0:16:02 > 0:16:05CLICKS CONTINUE
0:16:08 > 0:16:12The superpod spreads out into a wide hunting line,
0:16:12 > 0:16:14up to a mile across...
0:16:15 > 0:16:18..producing a wall of sound.
0:16:18 > 0:16:21CONSTANT CLICKING
0:16:30 > 0:16:33They're searching for their favourite prey.
0:16:36 > 0:16:38Lanternfish.
0:16:38 > 0:16:41They are the most numerous fish on the planet.
0:16:43 > 0:16:46But these small fish spend most of their time
0:16:46 > 0:16:51down in the deep ocean, way beyond the reach of dolphins.
0:16:51 > 0:16:54It's only when they come up to the surface to feed
0:16:54 > 0:16:55that they become prey.
0:16:59 > 0:17:01Once they've found a shoal,
0:17:01 > 0:17:04the dolphins use their sonar in a different way.
0:17:04 > 0:17:06SONAR BLASTS
0:17:06 > 0:17:09They stun the fish with loud blasts,
0:17:09 > 0:17:11then simply gather them up.
0:17:26 > 0:17:30As they feed, the dolphins work the underside of the shoal
0:17:30 > 0:17:34to stop their prey from escaping back into the safety of the deep.
0:17:55 > 0:17:56Within a few minutes,
0:17:56 > 0:17:59all that's left is a shower of scales
0:17:59 > 0:18:03drifting downwards to the ocean depths.
0:18:15 > 0:18:17The deep ocean is by far
0:18:17 > 0:18:20the largest habitat for life on Earth...
0:18:22 > 0:18:26..and home to some of the most bizarre hunters of all.
0:18:29 > 0:18:34Down here, food is much scarcer than at the surface,
0:18:34 > 0:18:39so deep-sea predators must do all they can to save precious energy.
0:18:48 > 0:18:52Waiting patiently, a viperfish.
0:18:52 > 0:18:55Special light-producing organs on its head
0:18:55 > 0:18:58entice prey towards fearsome teeth.
0:19:03 > 0:19:07Strange yet deadly jelly hunters also live here.
0:19:10 > 0:19:12Most simply drift,
0:19:12 > 0:19:16trailing tentacles loaded with lethal stings.
0:19:21 > 0:19:25Others, propelled by lines of beating hairs,
0:19:25 > 0:19:28glide gently through the darkness.
0:19:43 > 0:19:44Beroe -
0:19:44 > 0:19:47the top deep-sea jelly predator.
0:19:54 > 0:19:56They actively hunt other jellies...
0:19:59 > 0:20:01..like this ctenophore.
0:20:15 > 0:20:18To grasp its gelatinous prey,
0:20:18 > 0:20:23Beroe has special teeth-like spikes in its mouth.
0:20:37 > 0:20:42Many deep-sea hunters just hang in the abyss,
0:20:42 > 0:20:44saving their energy,
0:20:44 > 0:20:47luring their prey to come to them.
0:20:53 > 0:20:55Chiroteuthis.
0:20:56 > 0:21:01This deep-sea squid fishes for prey using long, sticky tentacles.
0:21:03 > 0:21:05Each has a glowing lure,
0:21:05 > 0:21:07pulsing to attract passing prey.
0:21:24 > 0:21:29A gentle twitch adds to the temptation.
0:21:56 > 0:22:01Down here in the darkness, this meal is a rare bonanza.
0:22:10 > 0:22:15The open ocean may be a vast blue desert,
0:22:15 > 0:22:19but like all deserts, it has oases.
0:22:27 > 0:22:30Scattered widely across this endless space
0:22:30 > 0:22:33are thousands of small islands.
0:22:37 > 0:22:40These are the summits of underwater mountains,
0:22:40 > 0:22:43which rise up from the sea floor many miles below.
0:22:51 > 0:22:55The seamounts deflect deep-ocean currents upwards,
0:22:55 > 0:22:58forcing nutrient-laden water to the surface.
0:23:06 > 0:23:10A busy oasis in the emptiness of the big blue.
0:23:31 > 0:23:35For potential prey, there's plenty of shelter amongst the coral...
0:23:38 > 0:23:41..and in the caves that are hidden beneath the reef itself.
0:23:52 > 0:23:55Small fish take refuge here,
0:23:55 > 0:23:57out of the reach of most of their predators.
0:24:00 > 0:24:01But not all.
0:24:03 > 0:24:05Lionfish.
0:24:10 > 0:24:12They're not built for speed -
0:24:12 > 0:24:16success here depends on delicate manoeuvring.
0:24:18 > 0:24:22Their strategy is to hide in plain sight,
0:24:22 > 0:24:25lulling their prey into a false sense of security.
0:24:33 > 0:24:36The lionfish's stripes are visually confusing,
0:24:36 > 0:24:40making it difficult for their prey to judge how close it is.
0:24:54 > 0:25:01Using its extravagant fins to hide slow and deliberate tail movements,
0:25:01 > 0:25:03it edges ever closer.
0:25:07 > 0:25:10It must get to within a few centimetres,
0:25:10 > 0:25:12close enough for a sudden strike.
0:25:25 > 0:25:26Got one.
0:25:37 > 0:25:41The deep-water currents that sustain so many residents
0:25:41 > 0:25:44also attract visitors to these oases.
0:25:49 > 0:25:51Silky sharks.
0:25:56 > 0:25:59They journey hundreds of miles between seamounts,
0:25:59 > 0:26:03using them as gathering places in the featureless ocean.
0:26:09 > 0:26:11They're joined by hammerheads.
0:26:16 > 0:26:19Both these sharks constantly travel
0:26:19 > 0:26:22between the Galapagos and other isolated seamounts
0:26:22 > 0:26:24in the Eastern Pacific.
0:26:30 > 0:26:33No-one knows for sure why they gather in such numbers,
0:26:33 > 0:26:38but some certainly come to these oases in search of food.
0:26:46 > 0:26:50A school of resident silversides cloaks the seamount.
0:26:52 > 0:26:54If these little fish stay close to the coral,
0:26:54 > 0:26:57the sharks won't be able to get at them.
0:27:17 > 0:27:21Other, more agile visitors are attracted by the potential feast.
0:27:24 > 0:27:25Striped bonito...
0:27:28 > 0:27:29..and golden trevalley.
0:27:36 > 0:27:40To get a meal, they'll need to drive their prey up and away from the reef
0:27:40 > 0:27:41into open water.
0:27:45 > 0:27:48As long as the silversides stick close to the sea floor,
0:27:48 > 0:27:50they should evade their predators.
0:28:12 > 0:28:16This time, the frustrated hunters will have to search elsewhere -
0:28:16 > 0:28:20there's never an easy meal in the open ocean.
0:28:33 > 0:28:37The Southern Ocean encircling Antarctica.
0:28:42 > 0:28:44The wildest seas on our planet.
0:28:47 > 0:28:52Here, it's the storm-tossed waters that bring nutrients to the surface,
0:28:52 > 0:28:54creating isolated patches of richness.
0:28:58 > 0:28:59Far from the calm tropics,
0:28:59 > 0:29:03this weather-beaten ocean is home to the albatross.
0:29:12 > 0:29:16Black-browed albatross are the same size as frigatebirds
0:29:16 > 0:29:18but three times as heavy,
0:29:18 > 0:29:21and so they need a totally different flying technique.
0:29:26 > 0:29:30Albatross have the longest wingspan of any bird,
0:29:30 > 0:29:33and that enables them to exploit the power
0:29:33 > 0:29:35of the Southern Ocean winds.
0:29:40 > 0:29:42First, they glide into the wind,
0:29:42 > 0:29:45harnessing its energy to give them lift.
0:29:48 > 0:29:52Then they turn and descend downwind, picking up speed.
0:29:59 > 0:30:02Soaring on wind fronts like this,
0:30:02 > 0:30:04an albatross can travel
0:30:04 > 0:30:07hundreds of miles of ocean in a day...
0:30:09 > 0:30:11..barely beating its wings.
0:30:16 > 0:30:19They often spend weeks at sea,
0:30:19 > 0:30:23searching for prey without ever returning to land.
0:30:35 > 0:30:40Food at last - a patch of krill close to the surface.
0:30:43 > 0:30:45Because the winds are so strong here,
0:30:45 > 0:30:48albatrosses can afford the extra weight
0:30:48 > 0:30:50of waterproofing oils on their feathers.
0:30:53 > 0:30:55They can duck-dive to no more than a metre,
0:30:55 > 0:30:59so they rely on the churning of the Southern Ocean
0:30:59 > 0:31:01to bring their prey up into range.
0:31:31 > 0:31:34Like all birds, albatross have to breed on land,
0:31:34 > 0:31:38but suitable islands are so few in the South Atlantic
0:31:38 > 0:31:40that most are heavily overcrowded.
0:31:45 > 0:31:50Steeple Jason - one of the largest albatross colonies in the world.
0:31:50 > 0:31:53ALBATROSS SQUAWK
0:31:58 > 0:32:02Nearly half a million come back here each year to raise their young.
0:32:11 > 0:32:13Adults share parenting duties,
0:32:13 > 0:32:16returning every few days to feed their chick.
0:32:25 > 0:32:31Feeding done, it's time to head out to sea.
0:32:37 > 0:32:40They need to make their way to the edge of the packed colony
0:32:40 > 0:32:42where there's more room for takeoff.
0:32:42 > 0:32:45CHICK CRIES
0:32:45 > 0:32:49Albatross are so heavy that they can only get airborne
0:32:49 > 0:32:51in places where the wind is strong enough.
0:32:55 > 0:32:57Using a special runway...
0:33:00 > 0:33:01..with a good headwind...
0:33:08 > 0:33:09..she's off.
0:33:19 > 0:33:24From the air, the ocean may appear featureless,
0:33:24 > 0:33:26but beneath the surface,
0:33:26 > 0:33:30a network of powerful currents is constantly on the move.
0:33:33 > 0:33:36It's these currents, more than any other force,
0:33:36 > 0:33:39that determine the distribution of life out here.
0:33:42 > 0:33:44A whole community of ocean drifters
0:33:44 > 0:33:47hitches rides on these rivers in the sea.
0:33:50 > 0:33:52Pelagic red crabs.
0:34:03 > 0:34:06They've gathered to feed on tiny floating plants and animals,
0:34:06 > 0:34:09a bloom of plankton fuelled by the currents.
0:34:20 > 0:34:24Fine hairs on their legs slow their descent...
0:34:26 > 0:34:29..and then, with a few flicks of the tail,
0:34:29 > 0:34:32they swim back up to continue feeding.
0:34:42 > 0:34:45The currents that carry these wandering crabs
0:34:45 > 0:34:49also serve as highways for the ocean's larger predators.
0:34:54 > 0:34:56Striped marlin.
0:35:01 > 0:35:03Beautifully streamlined,
0:35:03 > 0:35:07they can travel huge distances with minimum effort.
0:35:09 > 0:35:12These hunters patrol the boundaries between ocean currents,
0:35:12 > 0:35:14where their prey often gathers.
0:35:18 > 0:35:21Each predator has an incredible sense of smell,
0:35:21 > 0:35:24able to detect faint trails left by their prey.
0:35:29 > 0:35:33Somewhere out here is the big prize...
0:35:35 > 0:35:37..and hunters of all kinds are looking for it.
0:35:55 > 0:35:59Great shoals of fish are attracted to a plankton bloom.
0:36:01 > 0:36:04A single school of sardines can be many miles long.
0:36:10 > 0:36:15The fish swim tightly together - there's safety in numbers.
0:36:19 > 0:36:22Their defence relies on coordination.
0:36:27 > 0:36:30When attacked, the sardines move as one.
0:36:39 > 0:36:43Each fish instantly matches the movements of its neighbour...
0:36:45 > 0:36:48..and the whole shoal moves in synchrony.
0:36:55 > 0:36:59A lone sea lion can't keep up with their rapid reactions.
0:37:08 > 0:37:11Even when more sea lions arrive,
0:37:11 > 0:37:15they can't seem to break down the sardines' coordinated defences.
0:37:33 > 0:37:37With a shoal this big, the sea lions need to isolate
0:37:37 > 0:37:39a smaller, more manageable group of fish.
0:37:45 > 0:37:49But with so few predators, the fish still have the advantage.
0:37:55 > 0:37:59All the sea lions can do is keep the sardines at the surface
0:37:59 > 0:38:01and wait for others to join them.
0:38:11 > 0:38:13Tuna.
0:38:13 > 0:38:16Their arrival changes everything.
0:38:29 > 0:38:31Tuna attack from below,
0:38:31 > 0:38:34cutting off the sardines' escape route down to deeper water.
0:38:43 > 0:38:47Next to appear, shearwaters -
0:38:47 > 0:38:51excellent fliers, but also surprisingly agile underwater.
0:38:55 > 0:38:58With so many predators attacking from all sides,
0:38:58 > 0:39:02the advantage starts to shift away from the sardines.
0:39:22 > 0:39:24As the fish pack ever tighter,
0:39:24 > 0:39:28their shoaling strategy now makes it easier for the hunters.
0:39:53 > 0:39:55Copper sharks.
0:39:55 > 0:39:58They've scented blood in the water.
0:40:04 > 0:40:08Surprisingly, perhaps, the predators never attack one another.
0:40:08 > 0:40:11They work together to corral the ball of fish,
0:40:11 > 0:40:14taking turns to grab a mouthful.
0:40:23 > 0:40:25Common dolphins.
0:40:28 > 0:40:30As the shoal gets ever smaller,
0:40:30 > 0:40:34each sardine scrambles desperately to hide in the middle.
0:40:34 > 0:40:37But now, there's no escape.
0:40:56 > 0:41:01A Bryde's whale finishes off the feast -
0:41:01 > 0:41:05tonnes of sardines devoured in less than an hour.
0:41:17 > 0:41:19The predators melt away into the blue...
0:41:23 > 0:41:25..going their separate ways once more.
0:41:36 > 0:41:39This blue whale is still searching for a meal
0:41:39 > 0:41:42to satisfy its giant hunger.
0:41:45 > 0:41:46Being so large,
0:41:46 > 0:41:50it must catch an average of four tonnes of food a day.
0:41:55 > 0:41:59But many days may pass without feeding at all.
0:42:04 > 0:42:11It is their great size that enables blue whales to travel the furthest,
0:42:11 > 0:42:15roaming every ocean from the tropics to the poles.
0:42:15 > 0:42:17BLUE WHALE SPOUTS
0:42:29 > 0:42:32Trapped against the surface by fish,
0:42:32 > 0:42:34a dense patch of krill.
0:42:39 > 0:42:41This blue has finally found
0:42:41 > 0:42:44what it's been searching for for so long.
0:42:46 > 0:42:51A meal big enough to make opening its massive mouth worthwhile.
0:42:56 > 0:42:59The krill swarm is hundreds of metres across
0:42:59 > 0:43:01and packed tight.
0:43:09 > 0:43:12The whale lines up on its prey,
0:43:12 > 0:43:14targeting the densest part of the shoal.
0:43:55 > 0:43:59It takes so much effort to swim with a fully extended throat
0:43:59 > 0:44:03that the whale virtually comes to a standstill.
0:44:16 > 0:44:21The whale uses its tongue to force the water out of its mouth,
0:44:21 > 0:44:26trapping the krill on plates of hairy bristles that line its jaw.
0:44:30 > 0:44:33But it takes time to sieve so much water.
0:44:36 > 0:44:39And that gives more nimble hunters their chance.
0:44:54 > 0:44:58Blue whales may not be as agile as other hunters,
0:44:58 > 0:45:00but they don't need to be.
0:45:02 > 0:45:04In one giant mouthful,
0:45:04 > 0:45:07they can swallow whole swarms of krill.
0:45:59 > 0:46:02No other predator is better suited
0:46:02 > 0:46:07to exploit the scattered riches that the open ocean can provide.
0:46:11 > 0:46:14The blue whale -
0:46:14 > 0:46:18the greatest hunter in all the world's oceans.
0:46:55 > 0:46:59The open ocean created many challenges for the Hunt team.
0:47:01 > 0:47:05But none came bigger than trying to film blue whales underwater.
0:47:07 > 0:47:11Achieving this was to turn into a two-year mission.
0:47:13 > 0:47:16The crew teamed up with John Calambokidis,
0:47:16 > 0:47:19the world's foremost blue whale scientist.
0:47:21 > 0:47:25John gets crucial information from these harmless tags.
0:47:27 > 0:47:32But he can only observe blue whales for the brief time they surface.
0:47:34 > 0:47:37Well, part of this research and part of the reason
0:47:37 > 0:47:39that, er, we're working with film-makers
0:47:39 > 0:47:44is it gives us a unique chance to get scientific information
0:47:44 > 0:47:45we wouldn't be able to otherwise.
0:47:45 > 0:47:47So we are doing this under our research permit
0:47:47 > 0:47:50to get an insight into what they're doing underwater -
0:47:50 > 0:47:53how they're diving, how they're swimming, how they're feeding.
0:47:56 > 0:47:59Pictures of blue whales are rare.
0:47:59 > 0:48:01They're the biggest animal ever to live on the planet,
0:48:01 > 0:48:05but there are only a few underwater pictures that exist today.
0:48:05 > 0:48:07A few where you can actually see the animal.
0:48:07 > 0:48:10First, they have to find a blue whale.
0:48:10 > 0:48:13Well, I always feel really embarrassed, you know,
0:48:13 > 0:48:16because how can you lose the biggest animal that's ever lived, you know?
0:48:16 > 0:48:20But...er, while the whale is big, the ocean is even bigger.
0:48:25 > 0:48:26Just over here.
0:48:28 > 0:48:32The team's success will depend on good water visibility.
0:48:34 > 0:48:38Too murky, and the whale literally disappears into the gloom.
0:48:43 > 0:48:44No shot.
0:48:46 > 0:48:49The first year was blighted by poor visibility
0:48:49 > 0:48:51and the shoot ended in failure.
0:48:56 > 0:49:01Year two, and the sea conditions are much better.
0:49:04 > 0:49:06Oh, here he is, right here.
0:49:06 > 0:49:09Blue whales only surface for two to three minutes at a time
0:49:09 > 0:49:13before diving for up to 15 minutes.
0:49:13 > 0:49:16It's a narrow window for everything to come together.
0:49:16 > 0:49:18There's a bit of tricky manoeuvring here for John.
0:49:18 > 0:49:21He's got to try and get the boat
0:49:21 > 0:49:23ahead of the whale but not in front of it.
0:49:27 > 0:49:29Then David has to swim out
0:49:29 > 0:49:32and hope the whale passes close enough to get a shot.
0:49:39 > 0:49:41It's too far.
0:49:41 > 0:49:44It's a little too far that time.
0:49:52 > 0:49:55This year, the water is exceptionally clear...
0:49:58 > 0:50:01..but getting David in the right position still takes time.
0:50:03 > 0:50:05He went by, I definitely got a shot.
0:50:05 > 0:50:06It's not one of our best.
0:50:17 > 0:50:18Missed it.
0:50:21 > 0:50:22After weeks of effort,
0:50:22 > 0:50:24all the elements finally come together,
0:50:24 > 0:50:27giving David the chance of a lifetime.
0:50:30 > 0:50:34Like, I got down to about 25 feet. I knew that whale was out there.
0:50:34 > 0:50:38But, er...he just came out of the blue, right to me.
0:50:44 > 0:50:47I could see his eye, the details of his mouth,
0:50:47 > 0:50:51every scratch on his skin.
0:50:51 > 0:50:53And he cruised on by - it took forever.
0:50:53 > 0:50:57You know, they're so big - it just went by like a freight train.
0:51:02 > 0:51:04I saw his tail slide by.
0:51:04 > 0:51:07And he slipped back into the blue.
0:51:07 > 0:51:09It...it was awesome.
0:51:09 > 0:51:12That is awesome - I have never, of all my years of doing this,
0:51:12 > 0:51:14I've never got a shot like that.
0:51:14 > 0:51:15That was amazing.
0:51:16 > 0:51:19Images of blue whales underwater are so rare
0:51:19 > 0:51:25that this shot of one simply swimming by is a major success.
0:51:25 > 0:51:28But the crew need more.
0:51:28 > 0:51:30This series is all about hunting,
0:51:30 > 0:51:33and so, nice though it is to have that shot, to make a sequence,
0:51:33 > 0:51:37we've got to get shots of blue whales eating krill.
0:51:37 > 0:51:39And what we've got to wait for
0:51:39 > 0:51:41is when the krill actually comes to the surface.
0:51:41 > 0:51:44It might happen once, maybe twice a month.
0:51:46 > 0:51:49The crew come across an encouraging sign,
0:51:49 > 0:51:52from a rather unsavoury source.
0:51:52 > 0:51:55That's some whale faeces.
0:51:56 > 0:51:59So we've found a big whale poo in the water.
0:51:59 > 0:52:03Um, it's a good sign for us, we know that they're feeding here,
0:52:03 > 0:52:04so maybe they'll stick around.
0:52:07 > 0:52:10Finally, the crew find what they've been looking for -
0:52:10 > 0:52:12krill at the surface.
0:52:12 > 0:52:13Look at those birds in the water.
0:52:13 > 0:52:16So there's a small krill ball.
0:52:16 > 0:52:18We're going to go take a look at it.
0:52:18 > 0:52:20All right - remember, don't put me right on top of it.
0:52:20 > 0:52:22All right, ready? OK, the ball's right here.
0:52:22 > 0:52:24- Right here, right here. - Is it on the surface?- Yeah.
0:52:24 > 0:52:26- Good red?- Up at the top.
0:52:26 > 0:52:28- Got it?- Yeah, got it.
0:52:32 > 0:52:35No-one was prepared for what happened next.
0:52:36 > 0:52:40Right behind you! Hey, Hugh, here he comes!
0:52:40 > 0:52:41Oh!
0:52:43 > 0:52:45Massive surfacing.
0:52:46 > 0:52:49Oh, God - that's a shot. I bet you he got it.
0:52:50 > 0:52:52I bet you he got it.
0:52:52 > 0:52:53Oh!
0:52:57 > 0:53:00- MAN ON BOAT:- God, they're beautiful, aren't they?
0:53:00 > 0:53:03- What did you guys get? What did you guys get?- Oh, my God.
0:53:04 > 0:53:06Oh, my God.
0:53:07 > 0:53:11I still... I can't actually quite get my head around what I just saw.
0:53:11 > 0:53:14We were down there, Dave was filming the krill balls,
0:53:14 > 0:53:18and I just noticed, literally between his fins,
0:53:18 > 0:53:22this massive great whale just loomed out.
0:53:22 > 0:53:24David saw him, panned down.
0:53:24 > 0:53:26I don't know where it came from.
0:53:29 > 0:53:31Well, when I first looked down and I saw this whale,
0:53:31 > 0:53:33I was a little bit stressed out,
0:53:33 > 0:53:37because 95 feet of blue whale is going between my fins.
0:53:37 > 0:53:42He hooks around, comes up and just grabs a big mouthful.
0:53:48 > 0:53:50They're called blue whales for a reason,
0:53:50 > 0:53:51you just see them underwater,
0:53:51 > 0:53:54this bright, iridescent cobalt blue
0:53:54 > 0:53:56just pops out of the blue of the ocean.
0:54:00 > 0:54:01Finally, I get round to the other side,
0:54:01 > 0:54:04I go "OK, he left," we're like, "Phew! That was pretty intense."
0:54:04 > 0:54:06So I'm up trying to get just another shot of the krill
0:54:06 > 0:54:09and sure enough, wide open, he comes through one last time.
0:54:09 > 0:54:10I was kind of in the wrong spot,
0:54:10 > 0:54:13I had to do some serious evasive manoeuvres.
0:54:13 > 0:54:15But he comes through, closes his mouth...
0:54:15 > 0:54:17It was just amazing.
0:54:23 > 0:54:25The whole thing probably lasted ten minutes
0:54:25 > 0:54:29but it was hands down, without a doubt, no questions,
0:54:29 > 0:54:31the most intense, amazing thing that I've ever seen.
0:54:41 > 0:54:45To share the water and to look eye-to-eye with a blue whale
0:54:45 > 0:54:47is something I will never, ever forget.
0:54:50 > 0:54:53These shots give John a unique insight
0:54:53 > 0:54:55into the feeding behaviour of blue whales.
0:54:55 > 0:54:58Let's just look at the side of his mouth there.
0:54:58 > 0:55:00So, basically, the water flow, you'd expect,
0:55:00 > 0:55:02would be coming out the back there.
0:55:02 > 0:55:04Yeah, look at that little fold there,
0:55:04 > 0:55:06that is really interesting.
0:55:10 > 0:55:12That's a great view.
0:55:12 > 0:55:14That's fantastic.
0:55:14 > 0:55:18Notice the full rotation there. Oh, that is...
0:55:18 > 0:55:20And the full inversion.
0:55:20 > 0:55:22OK - that's, again, a unique chance
0:55:22 > 0:55:24to see a perspective we don't get to see.
0:55:27 > 0:55:29With this close collaboration,
0:55:29 > 0:55:33the team have filmed blue whales as never before
0:55:33 > 0:55:35and at last have started to reveal
0:55:35 > 0:55:38the secret life of the ocean's greatest hunter.
0:55:45 > 0:55:48Next time, the hunt is on out in the open.
0:55:50 > 0:55:52On the deserts and grasslands...
0:55:59 > 0:56:03..where hunters and hunted have nowhere to hide.