Film audiences who aren’t already claustrophobic might feel that way after watching The Chamber, a new thriller set almost entirely off the coast of North Korea in the cabin of an overturned submarine stuck at the bottom of the Yellow Sea. The plot — a looming conflict between the US and North Korea — is either poorly timed or extremely well-timed, given recent global events, but the real story is the classic moral quandary of how humans behave when trying to survive.

Mats, a Swedish submarine ship captain for hire (played by Force Majeure star Johannes Bah Kuhnke), gets entangled in espionage when his boss orders him to pilot an American special ops team to an undisclosed location in a rickety Cold War-era submarine called the Aurora. The American mission is led by the steely Edwards (Charlotte Salt), with Denholm (Elliot Levey) and Parks (James McArdle), rounding out the three-person unit. Before they submerge, Mats says, “This isn’t some fancy Navy Seal submarine. She ain’t a high-tech sporty thing.” Only Mats knows how to maneuver the old finicky sub, but his boss has agreed to let the Americans call the shots.

The film’s conflict comes from the team’s mysterious mission, which revolves around destroying what appears to be an RQ-170 surveillance drone that’s been hidden from the North Koreans in the Yellow Sea. When Edwards first spots the hidden drone, she marvels at it. “An RQ4, a global hawk UAV, a US unmanned aircraft with full targeting and surveillance capabilities. It’s a drone. Beautiful, isn’t she?” It becomes clear the she will go to any lengths to destroy the drone, even if they destroy the fragile submarine in the process.

In an interview with The Verge, writer-director Ben Parker says the premise of the film was inspired partly by the terror of drone strikes. “A drone that crashed in the ocean was where the kernel of the story came from. I’ve always been fascinated, or rather terrified, by drones. My first fascination, as a child, was of planes and aeronautics. I would have posters of planes on my walls.” But with the advent of remotely piloted, weaponized drones, his admiration turned to fear. “The disconnect of using unmanned aircraft for attacks is something that scares me. And The Chamber was really about all my darkest fears rolled into one, so I wanted the plot to revolve around the recovery of one of these drones.”

More than one of Parker’s fears makes its way into the film. He is claustrophobic, and the movie often feels that way as well. Jon Bunker, a concept artist on Gravity, conceptualized the close quarters of the submarine. The set was slightly larger than a real cockpit to make space for the camera, but the cramped space still feels oppressive — and on the verge of falling apart.

“I wanted it to be a raggedy submarine… to be fairly old and broken, because I saw, first hand, how advanced and safe modern subs were,” Parker says. “I wanted to be able to create a sense of dread in the audience, that this sub was like an old beat-up car, on its last legs and ready to collapse. And that this was the only option available. I think the use of an old, beat up ship must be influenced by my love of the Millennium Falcon as a kid. A reluctant hero, piloting a patched up tin-can.”

Parker also got inspiration and insight from his uncle, who was also a submarine pilot. “He was in the Special Forces, and he used to tell me stories about submarines. When I wrote the script, he was someone I could go back to and see what was plausible… He’d go down to great depths in these submarines and I was in suspense [to hear] what he found down there.”

As part of his research, Parker visited a NATO rescue submarine at Fort William in Scotland and was struck by the ordinary cameras on the exterior. “They were there for durability, not beautiful camera footage, so when it came to shooting the exterior viewpoints, I thought why not use the same thing they do on the real sub?” he says. “Using GoPros allowed us to get the look and with most maneuverability among the miniatures and sets. I really wanted to use on board GoPro footage for some of the interior action too again, to ramp up the realistic feel, but we didn’t end up using this in the film.”

Nor was The Chamber itself a high-tech or big-budget endeavor. With a budget of less than a million dollars, the crew had to be creative to film believable action sequences. “I didn’t want it to look low-res, but I did like the idea of confining things to a small space. It was even more fun. Four people stuck in a prison cell wouldn’t have been as dynamic,” Parker says.

Instead of CGI, the crew used old Hollywood tricks to create murky underwater sequences with GoPro cameras. “I realized I was emulating a lot of my B-movie inspirations, shooting models, higher camera rates, and then slowing it down,” says Parker. He cites the clever, sometimes outrageous camera work of filmmaker Roger Corman as an influence to create the effect of the ocean, and a way around budget constraints.

The film was shot in 23 days in a warehouse in Wales. “We constructed [the submarine] from the ground up ourselves. We had to film everything in sequence,” Parker says. As they filmed scenes where sub begins to fill with water, the actors had to stand in water for hours at a time, often while it was too cold or too hot. And then there was the unnerving pairing of electricity and water.

“We used visual effects where we needed to, but to also have real, practical effects wherever we could. And of course, being a ‘submerged’ thriller, I knew the limitations of mixing practical water and CGI effects. I wanted to try and do as much in-camera as I could,” he says. “We had a big net above the models with flour. Someone would tap the net, and little bits would come down with dust.”

For the final sequence, the cast and crew shot off the south coast of the UK near Devon. “We all jumped into the water and slowly drifted out to the sea,” says Parker of the last days filming on location.

The Chamber is in theaters, On Demand, and On Digital HD February 23rd.

https://www.theverge.com/2018/2/24/17043238/the-chamber-interview-film-submarine-drone-surveillance