The brilliant Blue Planet II is introducing Sunday evening audiences to the crazy and beautiful animals that live in the oceans. Yesterday, the programme visited brilliantly colourful reefs and showed their inhabitants - from team-spirited clownfish to predatory sharks - in incredible detail.

It took nearly four years of production to film the shots for the series, and when the team missed a spawning that only takes place once a year, they had to wait  another 12 months before they could capture the moment.  

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Last week, it was the turn of the cannibalistic squid, the squat sea toad or the hungry, hungry six-gill shark from the ocean's deep depths to star. 

Alongside the final segment of the programme showing how the shots were captured, the accompanying YouTube channel BBC Earth introduces the technology behind the production.

Filming sharks in protected French Polynesia

The protected waters of French Polynesia have become home to one of the highest concentrations of sharks anywhere on the planet due to the ban on shark hunting. 

Underwater cameraman Denis Lagrange dived down with his specialist film equipment and had the scary job of filming amongst all these predators. 

Filming a walrus on an iceberg

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The moving footage of a mother walrus trying to find a patch of sea ice for her cub to rest was a evocative way of showing the affects of climate change.

To get the shots, a specialist cameraman had to dive into the freezing Antarctic waters with a camera rig that weighs 50kg. It’s so big, it takes a team of three people to get it into the water.

However, the super-wide-angle camera means that the shot of the walrus and the iceberg could be captured perfectly.

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Sharks get too close for comfort

700 metres under the sea, you’re not too sure what you might find. In this case, the cramped three-person team in the submersible found some enormous six-gill sharks who took exception to being joined for dinner.

Luckily all the crew and their technology made it safely back up to the surface.

How to film in complete darkness

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Mobula rays are not habitants of the sea floor, but instead live just below the surface. However, to film them you need to overcome the challenges of filming in pitch blackness.

A husband and wife camera team did just that, and used the technology to showcase the bioluminescence in the ocean.

What submarines were used?

To reach 1000m beneath the waves, two submersibles were used in the filming of Blue Planet II. They live aboard the research and exploration vessel, Alucia.

Three people can spend six to eight hours in the eight-tonne vehicle, but it can take up to 12 hours to film the required footage. The bubble through which you see is made up of acrylic seven inches thick – protection you would like when heading down into the unknown!

One of the submersibles is fitted with 8K cameras in order to see the tiniest of creatures.

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Jon Copley, a marine biologist, passionately explains why it is so important to explore the deep ocean. 

"We don't yet know what we don't know", he told the BBC. "We can't explore it remotely", but it is absolutely necessary to physically visit these dark and unknown depths. 

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