In 2001 BBC America launched “The Blue Planet” to explore the inner depths of the world’s oceans and introduce audiences to a number of “characters” in the sea creatures that call those oceans their home. The world sat up and took notice — from England’s prime minister, who tweeted about the show, to the United Nations, who started a task force to tackle marine plastics. The show was nominated for five Emmys and won two. And now, more than a decade and a half later, BBC America is back at it again with “Blue Planet II.”

“Ninety-percent of the ocean is unexplored, so there’s so much more to do,” producer Mark Brownlow, who also produced “Planet Earth” in 2006, tells Variety.

This time around, Brownlow and fellow producers James Honeyborne and Orla Doherty set out with the explicit goal of looking for stories that were new and exciting and perhaps even pioneering.

“A year before we had our entire team out there talking to scientists and trying to break these groundbreaking stories. And then it’s a two-and-a-half year process trying to capture these theoretical stories on-camera, to varying degrees of success,” Brownlow says. “If you think that something is achievable, even if someone has never managed to film it before, then we’ll press the green light and go for it.”

One of the experiences “Blue Planet II” provides is witnessing a giant trevally leap out of the ocean (“like a missile!” says Honeyborne), turn in mid-air and catch birds. It was a phenomenon previously talked about but never before caught on camera. The “Blue Planet II” team heard the story “anecdotally” from a fisherman off an island in the Indian Ocean and decided, after talking with some other locals who also corroborated the story, that they had to document it.

“We set ourselves a high bar because we really wanted people who really know the ocean to learn things they didn’t know,” Honeyborne says. “We would like to think this is entertainment TV at the heart of the series with some characters you’ve never met before, but what you’ll love about it is it’s new; you’re learning stuff; it’s going to amaze you. Inherently that is educational, and to us, it’s about hopefully connecting people to life beneath the waves so we can come to care about it more and feel closer to it because that’s when we can make a positive influence.”

And that is not to say that the team shut down the idea of returning to an area simply because they may have seen it before. Doherty shares that they returned to the brine pool in “Blue Planet II” because the way they could film it now, with the additional research they had done and the new technology they were using, made it feel like they could tell a new story. “And we did. This eel showed up and did this toxic dance,” she says.

The “Blue Planet II” team is particularly proud of the characters they have been able to capture, of which the giant trevally is only one. Another is a dolphin that “knows the secret, individual medicinal properties of corals,” says Brownlow. And another still is the humboldt squid that hunts “900 meters off the coast of Chile. They go after the fish, and when the fish scamper, they turn on each other and go cannibalistic,” says Doherty.

Producers are also proud of the fact that nothing in their series is enhanced with CGI or other visual effects. All footage is captured in real time, with a combination of patience, fortitude, and technology.

“For us to be able to film those humboldt squid, the only way we could do that was to do our best to make ourselves invisible, which isn’t easy in a nine-ton bright yellow submarine. But the way we did it was by using this camera that we could just use the tiniest amount of light so we could not disturb their behavior,” Doherty says.

“Blue Planet II” shot on RED Dragon cameras, which are 4K, and the producers developed their own camera system and lenses. They often used a 24-inch megadome lens that would allow them to see both above and beneath the surface of the water in focus at the same time so, as Brownlow explains it, “you can see a walrus lying on an iceberg and the extent of the iceberg underneath.”

They also used rebreather systems that allow divers to go under for “much longer than you could on SCUBA,” adds Honeyborne.

“They don’t make bubbles, so they don’t make noise and they don’t make disturbance. You can hang with a fish for much longer. And it’s when you’re with them for three or four hours at a time that they just really let you see their character, and then this whole revelation of how sophisticated and intelligent they are starts to come out,” he says.

While at times “Blue Planet II” used remote-operated vehicles to dive even deeper than humans could, whenever possible they preferred to use human-operated cameras in order to be able to move and constantly capture the right “eye-level” with the animals.

“Before you can protect the ocean, you’ve got to care about it — that’s the fundamental thing,” says Honeyborne. “So we want to show people how wonderful this world is and how crazy and powerful the animals are. It will challenge you straight away because you start looking fish in the eyes and you realize they’re so much more intelligent than you realized. That’s what’s exciting to us: to be able to reveal the real characters of the animals and to be able to draw them to you.”

Not all tales on “Blue Planet II” are marvels of animals, though. Some, unfortunately, deal in the dangers to the animals through human waste, like plastics. Some animals are still getting entangled in plastics, while others are ingesting broken down pieces, which then become a part of the food chain — the consequences of which are still to be determined. The show does not shy away from these dangers because, as Doherty puts it, the ocean is key to our survival. “We need it healthy,” she says. “Its health is a link to everything else on this planet.”

“Blue Planet II” premieres Jan. 20 on BBC America.