BBC’s seven-part ocean documentary, “Blue Planet II,” was 2017’s most watched TV series in the United Kingdom, playing a part in Prime Minister Theresa May’s recent moves to take up the cause of marine plastic pollution. In China, according to executive producer James Honeyborne, it’s now been watched 225 million times. The Atlantic called the film, narrated by the venerable David Attenborough, the “greatest nature series of all time.”

This past Saturday, “Blue Planet II” debuted in the United States, and the filmmakers are hoping to see similar enthusiasm from U.S. viewers.

“We have a shared ambition to tweak the needle and just to move people’s feelings about the oceans,” said Honeyborne at a screening and panel held at New York City’s historic Explorers Club in January. “Many people tell us that the oceans are cold, dark, alien, remote. We don’t think of them like that.”

Among the film’s biggest achievements is its second episode, “The Deep,” which takes audiences to the deep sea and will air on BBC America and other stations on Saturday.

To date, only 5 percent of the deep sea has been mapped in detail, let alone explored by humans, and any film that connects mainstream audiences with the unique and bountiful biodiversity there is certain to challenge the public’s understanding of the boundaries of life on this planet.

As deep sea scientist Alan Jamieson wrote in a review of the episode in Nature Ecology and Evolution, it still takes a landmark documentary to capture the behaviors of many of the deep sea wildlife featured. (He took issue, however, with how this and other deep sea films characterize its habitat and wildlife as spooky, alien and less known than the surface of Mars. Today, even the deepest parts of the ocean also face threats from humans, which include seabed mining, plastic pollution and destructive fishing practices.)

The episode captures scenes such as bluntnose six-gill sharks feasting on a sperm whale carcass, an eel convulsing in shock after entering the intensely salty brine pools in the Gulf of Mexico and the first documentary film footage of Antarctica’s chilly, deep waters, where bioluminescent Antarctic krill rule. The scenes were put together from some 1,000 hours of shooting in the deep ocean, where producers leveraged cutting-edge filming techniques and knowledge of some 250 deep sea scientists to capture images, the episode’s producer, Orla Doherty, said.

While some scenes were about exploration, many, she said, were planned and storyboarded in advance. For example, even though what is termed a “whale fall” has never been studied in the Atlantic, she said, previous studies in the Pacific Ocean gave a sense of the incredible yearlong smorgasbord on its carcass that would unfold. Working with scientists, they found a falling sperm whale to film near the Azores.

“We wrote a script. We had some of those characters. We did not have seven six-gilled sharks come in and sort of rip it to shreds in front of our eyes. That wasn’t in the script,” she said. They tagged the carcass with a beeper and returned to it again and again over a period of 12 to 14 months, chronicling its slow decay at the hungry mouths of a succession of wildlife.

Working on many of the episodes’ dives with Alucia Productions, the nonprofit media company that hosted the New York screening, the filmmakers had the rare advantage of diving with two submersibles in tandem. One could provide lighting while the other vehicle shot the scenes.

“That means it’s not just like you’re putting a spotlight into the deep ocean. You’re actually creating a beautiful image,” said Honeyborne. “We knew that was going to be really important when it comes to how we feel about the creatures of the deep sea.”

Alucia, which worked on four episodes of the “Blue Planet II” series from its ships, M/V Alucia and M/V Umbra, was also tasked with rigging better underwater cameras that could film at those depths. “When you try to go down to 1,000 meters, usually you are filming [from] inside the sub and that really gives you a limited perspective,” said Mark Dalio, Alucia’s founder and creative director. (Alucia is the media arm of the Dalio Foundation’s Dalio Ocean Initiative.)

Instead, working with partners including the firms DOER (founded by oceanographer Sylvia Earle) and Gates Underwater Products, the team developed a camera housing that could be attached to submersibles and allow remote-controlled filming from inside, he said. After testing and several hiccups, including issues with freezing lens gears during Antarctica filming, it helped capture the episode’s footage.

In one remarkable scene filmed off the coast of Chile, a pack of giant Humboldt squid are busy hunting for prey. When the fish run out, however, they begin to prey on each other. Doherty said the footage uniquely captures their natural behavior in the deep, because previously they’d only been filmed in shallower waters. “You get the illusion that you’re seeing them in the deep sea, but you’re not really,” she said.

To film the scene, the team used light as a lure that mimicked bioluminescent jellyfish, based on a method pioneered by marine scientist Edith Widder to capture footage of elusive giant squid, according to Dalio. To ensure as little disturbance to their behavior as possible, the crew shined lights no brighter than an iPhone’s flashlight and used powerful camera sensors to film the squids’ behavior, Doherty said.

“Blue Planet II” has been an unusual experience, even for veteran deep sea scientists like Samantha B. Joye at the University of Georgia, who has spent years studying the deep ecosystem of the Gulf of Mexico and was involved in filming scenes of the area’s unique brine pool ecosystems. There are hundreds of these in the Gulf, she noted, but humans have explored fewer than 10 of them, despite their unique microbial life that could have applications in medicine or biotechnology. She is currently working on scientific papers from the expedition related to the expedition’s exploration of the Gulf’s “methane volcanoes,” where subsurface gas bubbles up into the deep waters. But the effect of “Blue Planet II” on public engagement is perhaps most important, she said.

“We write papers. We sit in a lab. … We spend a lot of time out on the water [and] under the water,” Joye said. “That doesn’t really do much to educate the public about the importance of the oceans. It teaches our peers what we’re finding, but it doesn’t provide a platform for engagement at this level that I think scientists need to be engaged at, especially now.”

The Dalio Ocean Initiative is following up on the film with more engagement efforts, hosting screenings at science centers and working on an exhibition at the American Museum of Natural History later this year. With BBC Earth, Alucia Productions also released a video series, “Our Blue Planet,” that goes behind the scenes of filming, interviewing the people involved in making the film.

“That’s also a way to inspire kids to want to become scientists – to want to get down and dive themselves,” Dalio said.