Blue Planet II

Indonesia is home to some of the world's richest coral reefs. On one such reef, in Raja Ampat, a broadclub cuttlefish demonstrates a remarkable ability to hunt crabs by hypnotism. Many cuttlefish are able to change colour using the millions of pigment cells in their skin, but this cuttlefish dazzles its prey by displaying ever-changing patterns and moving bands of colour over its body while closing in to make the kill. However, the cuttlefish must also be cautious of predators such as blacktip reef sharks that prowl the reef. Its talent for changing colour also help it to avoid becoming prey itself.

On an Indonesian reef, a cuttlefish has set its sights on a large crab as its next meal. Larger crab species, such as this one, equipped with powerful claws, pose a challenge.

A blacktip reef shark prowls the reefs of Raja Ampat in Indonesia. Sharks are one of the main predators of the broadclub cuttlefish that also hunt in these waters.

The leopard coral groupers of Australia's Great Barrier Reef have developed a unique hunting strategy by forming an alliance with a sympatric predator. A fully grown grouper is too large to access small crevices where prey hides, but this species has learned to collaborate with big blue octopus, which have the ability to reach into narrow cracks of the reef. The grouper communicates with the octopus by turning pale, performing a headstand, to indicate the location of the prey. As the octopus flushes out the prey, the grouper is able to make a catch every so often. This is a remarkable show of intelligence and teamwork between two different species, allowing them to share the rewards of their successful hunts.

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A big blue octopus on Australia's Great Barrier Reef shares its hunting grounds with a leopard coral grouper. Though the two animals compete for the same prey, they have learned to work together to hunt more successfully. The grouper turns pale and points its head downwards, indicating to the octopus the patches of coral in which small fish are hiding. The octopus is then able to reach into the narrow crevices that the grouper can't reach and nab the prey. Occasionally, it's the grouper that makes the catch when the small fish are flushed out into the open by the octopus.

In the vibrant underwater metropolis of the coral reef, sea cucumbers, such as this blackspotted sea cucumber, play the role of a diligent scavenger, recycling the waste of other reef inhabitants.

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Green humphead parrotfish play a crucial role in the maintenance of coral reefs. Their strong beak-like mouths are excellent at biting off chunks of coral, from which they can extract nutrients. They excrete the remnants as sand, contributing to the formation of the sandy seabeds on which the coral grow.

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Green sea turtles travel long distances to visit a specific column of coral known as Turtle Rock in Sipadan, Borneo. So many generations of turtles have come here that they have worn a hollow in its top. A turtle resting here is meticulously cleaned of algae, parasites and dead skin by blennies and surgeonfish. Long queues often form behind the current customer and squabbles occasionally break out as the turtles vye for position to be cleaned next.

The bicolor blenny performs a valuable cleaning service to the turtles that visit a particular rock on the reef in Sipadan, Borneo. These small fish meticulously remove algae, parasites, and dead skin from the turtles, while benefitting from a reliable and plentiful food source.

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Striated surgeonfish, alongside blennies, provide a valuable cleaning service to sea turtles that travel long distances to a particular spot on the reef in Sipadan, Borneo. These small fish meticulously remove algae, parasites, and dead skin from the turtles, while benefitting from a reliable and plentiful food source.

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On the reefs of the Red Sea, a family of bottlenose dolphins is resting after a night of feeding. While the adults sleep, the adolescent dolphins engage in play, inventing games such as "catch the coral." These games, though seemingly frivolous, may play a crucial role in developing the young dolphins' coordination and agility - skills they will need when hunting in the open sea.

The tides bring a rich supply of microscopic plankton in from the open ocean to the coral lagoons of the Maldives. Here, hundreds of reef manta rays come together to feed. They display a unique "cyclone feeding" behaviour, in which their huge three-metre wingspans create a vortex that further concentrates the plankton, allowing them to take in more food with each pass through their enormous open mouths. These aggregations are brief, however; as soon as the tide turns and the food supply diminishes, the mantas disperse from the lagoon.

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A lionfish patrols the sandy suburbs of a reef at night. Suddenly, the fish is attacked by a giant carnivorous worm, a bobbit, that had been lying in wait, hidden just beneath the sand.

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The bobbit worm is a giant metre-long carnivorous worm that lurks just below the sand in the reefs of the Lembeh Strait. At night, the poor visibility enables the bobbit to ambush even large prey, such as lionfish, with its razor-sharp jaws. By day, however, successful hunting can be complicated by the cooperative behaviour of monocle bream. When these fish identify a hiding bobbit, they work together to blow away the sand concealing the worm, which neutralises its element of surprise.

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Dawn on the sandy suburbs of the reef brings more visibility, and safety from predators, for fish like Peters' monocle bream. Predators such as carnivorous bobbit worms that lie in wait just below the sand are more easily spotted by these small fish. When they do, instead of fleeing, they cleverly band together to expose its hiding place. Working collectively, they blow away the sand concealing the worm, effectively neutralising its element of surprise.

A saddleback clownfish family takes great care of the carpet anemone that they call home. The family is led by a dominant female, who directs the smaller males to kep the anemone clean of debris. Here, on the sandy flats of Pulau Mabul, there anemone isn't rooted to one spot and is easily pushed around by the current. So, when the matriach is ready to lay her eggs, her subordinates must find a suitably hard and heavy object for her to use. In their quest to find a safe nursery, the clownfish carefully consider anything the current brings into their vicinity, from the shell of a hermit crab to a discarded plastic bottle, before finally wrangling a coconut shell into the safety of the anemone. Once the eggs are laid and fertilised, the male takes on the responsibility of tending to the eggs until they hatch.

Haddon's sea anemone is the preferred host of saddleback clownfish. Its poisonous tentacles offer them protection from predators and, in return, the clownfish ensure the anemone is free of debris.

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A white-spotted hermit crab shares its home on the sand flats of Borneo's Pulau Mabul with a family of saddleback clownfish. The fish, in search of a hard and heavy object on which their matriach can lay her eggs, attempt to move the crab's shell closer to their host anemone but are surprised to see it already has an owner! The hermit crab lumbers away.

Thousands of camouflage groupers gather together on reefs of the Fakarava Atoll in French Polynesia to breed. Each male jostles with his competitors to get in prime position next to the egg-laden females. When the conditions are just right, under the light of the full moon, the females suddenly spring into action, releasing their eggs directly into the water. What follows is a frenzy of activity, in which the male groupers rush to fertilise the eggs with their sperm. So intent are they on breeding successfully, that the groupers become easy prey for the hundreds of prowling reef sharks that this annual event attracts to the reef. Though the majority of the fertilised eggs will consumed by predators, enough will survive and find new reefs to call home.

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Every year, Fakarava Atoll attracts thousands of groupers that gather to breed in mass spawning events. These events attract predators, such as grey reef sharks, which assemble in their hundreds and wait patiently alongside the male groupers for the females to begin spawning. Anticipating a feed opportunity, the grey reef sharks begin close in, just as the first females begin to release their eggs. Amid the chaos and with the prey entirely preoccupied, the sharks are able to easily pick off individuals from the shoal.