When Josh Hartnett was doing research for the role of Calvin Penney — a Newfoundland fisherman who encounters a mysterious force off the shores of his hometown — he learned that, as in Below (now streaming on Netflix), there are plenty of secrets beneath the sea’s surface.

“All that mysterious-creature stuff doesn’t feel outside the realm of possibility when you hear stories from real fishermen or people who spend a lot of time on the sea,” says Hartnett. “They always have a story of something that they can’t explain.”

The ocean, he adds, is “so vast” and there are many parts that haven’t been fully explored. “It’s kind of wonderful that we don’t know everything about our entire planet yet,” Hartnett says. 

Jan Thijs/Netflix

In the six-episode thriller from creator Jesse McKeown (a writer on The Umbrella Academy and 19-2), Hartnett plays Calvin, a villager in the fictional town of Snook’s Arm who is haunted by his father’s unexplained death decades ago. When an unidentified sea creature begins terrorizing his hometown, Calvin — a gruff but intensely loyal father of three — must fight to keep his close-knit community together.

“I’ve always loved Josh Hartnett as an actor. I think there’s a stoicism and strength about him,” McKeown says. “The more I found out about him, the more it made perfect sense [for him to play Calvin] — he’s got four kids of his own, he’s very much a family man, and he’s from Minnesota, which is almost Canada. I knew that he would get it.”

Hartnett dug deep into Newfoundland’s rich history and culture, spending time with local actors to capture the day-to-day realities of Snook’s Arm. On one occasion, he headed to a fish bake with a fellow cast member, and the pair grabbed water from the ocean, made a fire, and cooked lobsters in a pot. 

Jan Thijs/Netflix

“He told me all these stories,” Hartnett says. “He had so much knowledge of the history of the island and the people, and he did lots of different jobs — like most people do in Newfoundland. He writes books, he writes plays, he was a history professor, I believe, and now he is an actor as well.” 

Hartnett also tuned into a long-running local  radio show, The Broadcast, every day, studying the dialect and learning the pain points of Newfoundland fishing.

“There was a huge cod stock there for centuries, and they had been kind of over-fished by these huge multinational corporations,” he says. “The people who really suffered were local fishermen, because they were also not allowed to fish. Overnight, suddenly these people had lost all of their income, but also their identity.”

To further submerge himself in life on the water, Hartnett got to know some local fishermen and learned how to tie fishing nets. He forged real-life bonds with the actors who star as his onscreen children — Charlie Heaton (Wade Penney), Ruby Stokes (Mary Penney), and Rohan Campbell (Jay Penney) — and the foursome would frequent The Duke, a local eatery, for fish and chips. They all shared the same dialect coach, to make sure that it sounded like they were from the same family. 

“You are shooting for five, six months away from family, and you’re shooting in these hard locations,” says Heaton. “It’s exhausting, and that’s why I loved watching Josh. He’s such an incredible number one, such a professional, but he also just wants the work to be good.”

Heaton adds that Hartnett really revealed his devotion to the character and the series towards the end of production. “There are some scenes at the end of the series on the boat. I didn’t know Josh had taken boating lessons … I didn’t really know how to ride this boat, and the support and care that he gave me through those scenes was really cool.”

As it turns out, Hartnett — a native of Minnesota, hundreds of miles from any ocean — truly discovered a new affinity for the sea, spending time on a little boat watching humpback whale migration during the first few weeks of filming. 

“You could see their flukes, and they’d do this little thing where they wave their fins at you; it was incredible … they’ve been traveling that same migration pattern since before World War II,” Hartnett says. “It’s extraordinary to feel that connection to the sea.”

Watch all 6 episodes of Below now.