The new film Underwater follows a group of researchers who are stationed on a drilling station seven miles below the ocean’s surface when an earthquake strikes, flooding their facility. The team is forced to don underwater suits and walk across the ocean floor to a distant abandoned oil rig. As they set off on their journey, they find themselves being hunted by a mysterious sea creature.

Watch as the film’s director and stars Kristen Stewart, John Gallagher Jr., and Jessica Henwick describe what it was like to walk in 140-pound suits and film in massive tanks to make the thriller:

While Gallagher and Henwick opted to take scuba lessons in preparation for the film, Stewart, who has said she is “scared of swimming,” skipped the classes due to her fear.

However, this might have only added to the authenticity of Stewart’s acting in the film.

“We didn’t want to fake it,” says Stewart. “We wanted to get as close to real as possible.”

Underwater is in theaters now.