What’s it like to shoot a movie underwater? In the ‘Last Breath,’ ‘none of it was faked.’

In Last Breath, the ocean is terrifying. It’s claustrophobic despite its expanse, threatening to kill the people most familiar with it.

The movie is based on the true story of deep-sea divers who fought to rescue a crewmate trapped hundreds of feet beneath the North Sea, a part of the Atlantic Ocean that’s notoriously dangerous. Footage of its treacherous waves went viral on TikTok in 2023.

Since so much of the film takes place underwater, the production tapped Ian Seabrook as its cinematographer. Over nearly 30 years he gained a stellar reputation for his underwater camera work in movies and TV shows like I, Robot and Shōgun.

Finn Cole and Simu Liu, who play divers in the film, were extensively trained to shoot their own underwater scenes safely — a rare feat for actors, Seabrook told Yahoo Entertainment.

“It’s not very common, to be honest with you,” he said. “I’ve worked with plenty of actors who all say, ‘Oh yeah, I got certified in Hawaii, I’m good.’ No, this is completely different.”

There’s a lot going on in the water. They’ve got to act, for one, and dive safely. There are divers around specifically to make sure the talent is safe and people making sure the “umbilical” source of oxygen stays secure. They each had communication systems with which the film’s director, Alex Parkinson, could speak with them. Seabrook is also there with his camera rig.

“I was shooting and operating the camera, so I was with them the entire time. Sometimes, I would do a little bit of jazz and sort of zip around,” Seabrook said. “We did five or six one-hour dives per day.”

The film was shot at night to mimic the darkness that would engulf real-life saturation divers, adding to the claustrophobic feeling. The actors had strict rules about how much time they would spend under water.

“Once you put the mask on, you don’t have peripheral vision. As an actor, if you’ve never put a dive helmet on and you realize you can’t get out of all this equipment quickly, you’ve got to have pretty good nerves,” Seabrook said.

The crew discussed having professional divers act in the underwater scenes, then replacing their faces with those of the actors using visual effects, but Seabrook was “opposed to that idea entirely.” Cole and Liu were up for the challenge.

They went through an intense, week-long program led by the film’s dive supervisor, Abigail Borg, whose father had been a North Sea saturation diver. Cole’s father was an avid scuba diver, so he had some experience. Seabrook said there was “more concern” with Liu since he had less experience, but he gradually fell in love with diving.

Seabrook wasn’t always a diver either. His career began as a still photographer, but he became certified as a diver at the Great Barrier Reef in Australia. He began photographing marine life, and his career evolved from there.

“There was no real outlet to learn how to do this job, so I just figured it out. You get to this precipice in your life when you’re 25 or 26 years old, when you have to decide what you want to do with your life, and I had one of those epiphanies,” he said. “I was enjoying the surf along 90 miles of deserted beach in New Zealand when I thought … ‘well, I really like photography and I really like films, so I’ll become an underwater cinematographer.”

He picked up odd jobs on film sets but remained “obsessed with all things water” until more opportunities presented themselves. Now he’s one of the go-to experts in his field.

“Every film has its challenges. Last Breath had a lot of them, and everybody was pushed against the wall in some way, shape or form,” he said. “Every department didn’t have enough time and they didn’t have enough money … but on a picture like that, it had to be accurate.”

“None of it was faked,” he added.

Last Breath is currently in theaters.