We're hooked on ground-breaking nature series Blue Planet II, which took over four years to make, involved 125 expeditions, visits to 39 countries, and 4,000 dives that clocked up 6,000 hours spent underwater. We've seen bird-eating fish, surfing dolphins and had a stunning look at what lies beneath in the deepest, darkest oceans. To get the astonishing footage, the Blue Planet II team used the latest technology and even created their own specialist equipment to capture new landscapes and previously undocumented animal behaviour. Here we look at some of the tech that has given us a new look at the oceans.

Executive producer James Honeyborne told loveEXPLORING: "Perhaps the most exciting aspect of making this series has been that to best deliver new insights. We’ve not just been reporting the latest findings of marine biologists, we have joined forces with them, making discoveries together." Breakthroughs in marine science and cutting-edge technology allowed the team to explore new worlds and reveal the very latest discoveries. "We can stay submerged deeper, for longer, and in doing so, we have discovered that we have more in common with, and are more connected to the ocean than we ever imagined."

Revolutionary technology including submersibles allowed the Blue Planet II team to enter new worlds and film previously unknown behaviours in ways that were impossible 20 years ago. One of the most magical and otherworldly places that the team were able to film in was the deep ocean, which Honeyborne described as the ocean’s “final frontier” and "Earth's inner space”.

By using high-tech submersibles carrying ultra HD and extreme low-light cameras, The Deep episode plunges the viewer into the extreme depths to witness some of the ocean's weirdest creatures. In one of the series’ many firsts, they were the first people to get a manned sub down to the deep sea (3,200 feet underwater) in Antarctica. “This is our sci-fi film,” said series produver Mark Brownlow. “We spent more time in subs on our first shoot than in the entire original Blue Planet.”

The team spent two years preparing for this record-breaking expedition aboard the scientific research vessel MV Alucia to bring two submersibles – Deep Rover and Nadir – down below the icebergs of Antarctica. “After 1,000 hours in submersibles, Blue Planet II turns the spotlight on creatures so alien they could have come from outer space. It’s said we know less about the depths of our own planet than we do the surface of Mars,” explained Honeyborne.

Some creatures, such as the Midnight Zone's fearsome-looking fangtooth, were actually filmed in a special chamber aboard the research ship. According to Orla Doherty, producer of The Deep, some extreme close-ups of tiny creatures were painstakingly captured by a macro-camera manipulated on the submarine’s arm while others were achieved in collaboration with scientists. They collected the creatures using a manipulator arm and placed them in a dark refrigerated chamber. “It’s into that dark, cold room that we sent our camerapeople," she says.

In another first, Blue Planet II includes the first submersible dive into the squid zone. Once again, working from science and exploration vessel the Alucia, the Deep team and scientists mounted an expedition off the central coast of Chile to film hunting packs of humboldt squid from a submersible. They captured astounding footage of the terrifying-looking cephalopods preying on lantern fish at a depth of 2,624 feet – and even turning on each other and the cameras.

Some encounters were a little too close for comfort, particularly when several bluntnose sixgill sharks attacked the vessel as they arrived to feed on the carcass of a sperm whale near the Azores in the Atlantic Ocean. The astonishing footage of these large sharks that conserve their energy in the desert of the deep sea was taken at a depth of 2,300 feet from inside Lula, a submersible of the Rebikoff-Niggeler Foundation. It was a hair-raising moment for the crew.

Important imaging breakthroughs included the use of low-light and infrared cameras during night shoots and in the perma-darkness of the deep. “Low light technology is moving on so fast that we have scenes we have only just filmed because the technology didn't exist the year before,” said Brownlow. The use of two extremely light-sensitive cameras allowed the team to film spectacles such as the bioluminescence, or sea sparkles, produced by mobula rays as they feed and stir up plankton.

Infrared underwater cameras also allowed the film crew to capture some extraordinary behaviour that had never been seen before, including what Brownlow describes as “a horror sequence” with the bizarre bobbit worm in Indonesia. “If we’d shone a white light on this nocturnal ambush predator, it would have just stayed in its hole,” explained Brownlow. “But it can’t detect infrared light.”

Jonathan Smith, producer of the Coral Reefs episode, says cameraman Hugh Miller built a “one-of-a-kind lighting system” to capture the bobbit worm at work. “It was capable of illuminating an area underwater that could be detected only by a specially-adapted camera and was invisible to us. So the team would not be able to see anything down there themselves. Diving re-breathers would allow them to noiselessly sit on the seabed for many hours as they began their stakeout in the pitch black."

This rebreather technology – ex-US military diving tech – was revolutionary to the filming, allowing the team to stay in situ for longer with no bubbles or underwater disturbance. "For the first time, we can be underwater, staking out and just sitting and observing. Before you’d have had only 45-minute dives. Now we’ve got three-hour dives which is just revolutionary,” said Brownlow.

To achieve some of the series' most incredible shots, including that of a mother walrus and her calf sitting on an iceberg in the Arctic, a bespoke lens was required. In collaboration with camera housing developer Gates Underwater Products, the team built a huge, domed port measuring 23 inches across that allowed them to film both above and below the water at the same time.

“It allowed us to shoot split screen shots at the water surface, keeping the world both above and below in clear focus. That’s never been done with a video camera and it gives us our own distinct look,” said Brownlow. Here cameraman David Reichert is pictured using the bespoke mega-dome lens in Svalbard in the Arctic.

Another technological first allowed the team to get up close and personal with tiny fish and create an all-new immersive experience for the viewer while filming in the coral reefs of Australia’s Great Barrier Reef. “We also built underwater probe cameras consisting of a barrel of lenses with a tiny front element that allows you to film small reef fish right inside the coral cracks,” explained Brownlow.

The new technology allowed them to capture incredible footage of the coordinated hunt between coral grouper and octopus, which use their tentacles to get into the reef and help flush the little fish out. “With the underwater probe camera we managed to get inside the reef – and you’re looking around the reef like you’re a little fish with these octopus tentacles coming down all around you. You really feel like you’re experiencing this behaviour,” said Jonathan.

Innovations in equipment such as underwater sliders, motorised macro positioners, and scope lenses enabled the filmmakers to get inside the coral reef and “show it from the perspective of the critters that inhabit it,” writes one of the series cameramen Roger Munns on his blog. “That said,” he continues, “the majority of the filming was still done on a traditional underwater camera setup, using a housing from Gates Underwater Housings and a Red Dragon 6K camera."

“Red cameras have high dynamic range and are capable of shooting HDR and slow motion. Along with using bubble-free rebreathers, to be less intrusive and spend more time underwater, these technical advances mean that we are now able to shoot underwater in a very cinematic style, similar to topside wildlife film makers,” writes Munns.

Blue Planet II also deployed UHD drones to document some previously unknown animal behaviour including that of sea lions off Isabella Island in the Galápagos. The drone’s unique perspective allowed the team to capture the incredible footage of the sea lions driving yellowfin tuna from the open ocean into their cove, forcing them to beach themselves. Previously, aerial shots for the original 2006 series were shot on 16mm celluloid film, using helicopters.

Drones also captured the "cyclones" created by chains of feeding manta ray in Hanifaru in the Maldives. As plankton levels became dense as many as 150 rays were filmed looping around to form a kind of cyclone. This behaviour was only scientifically described in 2017 and filmed for the first time from the drone by the groundbreaking series.

Some of the most intimate footage involved getting the animals to do the filming themselves. In collaboration with scientists, the team built suction-cup cameras that could be attached to the backs of large cetaceans and sharks to show the action from their point-of-view. One was attached to a sperm whale in Dominica as it dived into the abyss hunting for squid. Another was attached to an orca as it hunted herring in Norway’s Arctic, taking the viewer right into the heart of a giant baitball.

Another suction cam was deployed on the back of a pregnant whale shark as it travelled through the Galápagos archipelago. The cameras were fitted with sensors that recorded speed, temperature, salinity, duration and location. They were designed to fall off after 30 hours where they could be retrieved and the astonishing footage finally viewed by the crew.

The team, working with in-house designer Mohan Sandhu, built a ‘mo-co’ rig in British Columbia, Canada, to film a rock pool in timelapse. As the tides rose and fell around it, the rig kept filming and its steady tracking timelapse revealed the amazing underwater life of a rock pool as it had never been seen before.

A bespoke solution was also required to film fast-moving yellowfin tuna and huge shoals of spinner dolphins as they charged at great speed through the open ocean near Costa Rica. The team built a camera that could be towed behind a boat, allowing them to keep up with the torpedo-like tuna as they travelled at speeds of up to 40 miles per hour.