In 2018, filmmakers Jimmy Chin and Elizabeth Chai Vasarhelyi were glued to the then-unfolding story of Tham Luang cave rescue. Though the around-the-clock coverage enthralled them, the married, Oscar-winning partners found themselves wondering how they would feel if their own children were trapped: What would that purgatorial limbo be like? 

That question spurred them to chase the story, which they would eventually piece together, from the divers’ point of view, in their latest documentary “The Rescue.” As Chin told The Daily Californian in a recent interview, it wasn’t an easy process. Plus, they had no idea what they were looking at. 

“We didn’t even completely understand the intricacies of what actually happened,” Chin explained. “We were just really interested in what happened, how it happened, the decisions that were being made.”

The directors wanted to tell the divers’ story, but even that was a challenge, further complicated by a pandemic. The divers are a group of, more or less, weekend hobbyists — guys with regular nine-to-fives (from electricians to meteorologists), and a very dangerous side gig that happened to make them the only ones capable of rescuing the Wild Boars. 

“All of a sudden, they’re thrust into this position where they have to make decisions that normally are put on professionals and highly specialized professionals,” Chin said. 

Reconstructing their days-long efforts would be more difficult. The main problem? Finding any footage. The filmmakers had little to go off of, and the project ultimately fell to two different options: animating the whole rescue or recreating it. The two settled on the latter and invited some of the divers to a studio where they reenacted the rescue step by step, down to the equipment used on the day. 

“We really just wanted to see the divers demonstrate what they did, and authenticity is hugely important to us,” Chin said. “Really, it was an exercise of saying, ‘OK, show us exactly what you did in this moment. … Who is there? How many tanks were you carrying? How did you maneuver the kids?’”

But the problem of how to represent the rescue without any footage quickly turned on its head. Chin and Vasarhelyi learned the Thai Navy SEALs, who had run the rescue operation, were sitting on a trove of never-before-seen footage from the rescue. 

“Chai (Vasarhelyi) flew to Thailand to get that footage (and) we thought like, ‘OK, maybe there’s like 90 minutes, and we’ll get like a minute out of it,’” Chin said. 

It ended up being 87 hours of unfettered access, shot from a GoPro that one of the divers had worn. The Thai Navy SEALs didn’t use UPS — they sent a small delegation to the directors’ studio in New York, where they locked the place down before showing the footage. Out of that, about 15 minutes ended up making it into the film, which had been nearly finished by this point. 

“So we basically had a movie, and had to break the movie (and) recut a lot of it. It just meant we didn’t sleep much this summer,” Chai joked.

The process wasn’t made any easier by the messy process of translating audio from the footage. 

“There were scenes that took three hours to translate three minutes, because it’s in Thai military lingo and Thai military slang and even the translators were having a really hard time,” Chai recalled. “So you take three minutes times three hours and you multiply that by almost 90 hours.”

Yet, the taxing process was essential to the film. Though Chin dubbed it a Herculean task, it was also part of the job. The footage brought a crucial element to the film that had evaded recreation.

“(It) was really critical in being able to show what it would look like inside the cave and how big the scope of the operation (was),” Chin said. 

The footage opens up a completely different side of the story — the army of volunteers and soldiers who made the rescue possible, the mechanisms the multinational team came up with to ferry the children out of the cave. While the addition of real footage alleviated some pressure from the filmmakers, a raging pandemic had brought its own stresses. 

“We had to do all the interviews via Zoom,” Chin recalled. “We had local crews setting up to shoot with (the subjects), but then we would do the interviews and it’d be like four in the morning where we lived and late afternoon for our subjects or whatever time zone they were in.”

Chin, Vasarhelyi and their editor, Bob Eisenhardt — who had worked with them on “Meru” and “Free Solo” — found the process incredibly rewarding: “We all looked at each other and said, ‘This is the hardest film we’ve ever made,’ … The constraints actually really push us creatively. And that’s part of the challenge, but also part of the fun.”

“The Rescue” premieres Oct. 15 and is playing at Landmark’s Shattuck Cinema.