When “The Devil’s Mouth” director Jeff Wadlow met the cast of his bloody shark movie, he made one thing clear.
“‘Listen, this is going to be the most physically demanding job you’ve ever had. Not just because of the stunt work and all the underwater work, but the fact that when you have a simple dialogue scene, you’re going to be treading water,’” Wadlow recalls telling Kathryn Newton, Lana Condor and the rest of the ensemble.
Written by Aja Gabel and Myung Joh Wesner, “The Devil’s Mouth” was named to the Black List back in 2019. Newton and Condor lead the cast as Sara and Max, two best friends whose friendship is tested after they get trapped in a freshwater cave — along with the rest of their college buddies, played by Gavin Casalegno and Tommi Rose — while taking a trip to Thailand.
Of course, things get complicated when a bull shark enters the scene. In order to prep for the intensive shoot, the actors spent two weeks treading water, doing breath holds and training with real kayaks. Besides one stunt where Newton’s character had to hop off a 35-foot cliff into a shallow pool of water, all the actors were game to do their own stunts — safely, of course.
“All the rock climbing, diving, underwater work, breath holds, getting dragged around on winches, that was all them,” Wadlow says.
Known for helming lower-budget horror films for Blumhouse like “Imaginary,” “Fantasy Island” and “Truth or Dare,” Wadlow was first approached about directing the film during a meeting in which he was laser-focused on pitching his dream “G.I. Joe” trilogy.
He had some hesitations when, instead, the words “shark movie” were mentioned.
“I said, ‘I really don’t want to just do a shark movie unless there’s something new,’” Wadlow recalls. Then when he heard about the one-location aspect of the film, his creative juices began flowing, and he did a rewrite on the script.
“Now we’re talking about an intersection between the shark movie genre and the claustrophobic horror movie,” he says. “I was blown away by how good it was because the character dynamics were complex and interesting. There’s a really nuanced investigation of female friendship.”
Below, Wadlow breaks down casting Newton and Condor against usual type, how his team built 13 sets on two soundstages to pull off the illusion of an endless cave in Thailand, and why “The Devil’s Mouth” is “the hardest movie” he’s made to date.
Talking about casting this friend group, what made Kathryn and Lana perfect for this central dynamic?
What’s funny about casting this film is both Kathryn and Lana thought they should be playing the other part. And you can kind of see it! Having made the movie, I only see Kathryn as Sara, and I only see Lana as Max. But on the page, the characters were sort of similar to characters that they had played before. I ultimately think that made the movie so much more interesting because it forced Kathryn to stretch and grow and define a quieter character to play. She normally plays really out-there dynamic characters, and Sara’s got an internal journey; Lana usually plays like the good girl, this was a chance for her to play someone with a little more bite. They both really rose to the challenge and did it together. They became best friends while we were making the movie. We shot this whole thing in Thailand. Thailand is so far away from America that if you leave from the East Coast, you go through the Middle East, and if you leave from the West Coast, you go through Japan. It’s literally on the opposite side of the planet, and so there were no long weekends going home. Once we were there, we were all there, and it was a Thai movie. There were about less than a dozen Westerners working on it.
How did you go about finding the cave? What were the biggest logistical challenges to filming inside?
It’s the hardest movie I’ve ever had to make. I mean, in 85% of the movie, the characters are swimming in water. Movie cameras in water do not get along, as we all know! And just like casting this movie, I had this crazy curveball at the last minute where it was written for Mexico and we were going to shoot in the Dominican Republic. I was 10 days away from leaving and the studio calls me up and says, “Hey, some sound stages and a crew just became available in Bangkok. Can you shoot Thailand for Mexico?” And I was like, “Well, that’s bonkers. What are you guys talking about? That would be so challenging and I don’t really see the point.” And on top of that, I’m allergic to peanuts! I can’t go and spend six months in Thailand, I will probably die. I’m being serious, I go into anaphylactic shock, and they’re like, “We’ll get you a second assistant whose only job will be to feed you, make you dinner reservations, keep you alive and get your driver, in addition to your U.S. assistant!”
I started thinking about the soccer team that got lost in the flooded cave system in Thailand, and how that was in our collective consciousness at the time in the zeitgeist. And I started doing some more research on freshwater cave systems in Thailand, and it started to feel a little bit more dangerous — a little bit more off the beaten path, a little bit more exotic, and I thought that would increase the credibility of what transpired. If it was just a system that tourists went to all the time in Mexico, for them to have gotten into this kind of trouble seemed a little less plausible. It also seemed like help would be there a lot sooner. But suddenly, you start setting it in a remote part of Thailand, it just feels further, more out the realm of these characters’ normal worlds.
How did you approach filming the caves and meet the challenge of this one location?
I wanted there to be this increasing sense of claustrophobia, so I started really wide and big. I wanted to make the trip look awesome and fun, and the location seem beautiful and appealing. I didn’t want the audience to ever go like, “Why are these people on this trip? This seems like a bad idea.” I wanted it to be obvious why they’re on the trip. It’s an amazing place to visit. Then I wanted to go into real caves that were mysterious and beautiful and not foreboding at all. I wanted the audience on the adventure, so I found real freshwater caves where rescue divers train. And then once they go around the corner, I went on a soundstage because shooting this movie in a real cave would be impossible. Forget just the lighting — the stunt work and safety issues would be massive. So once they’re in the cave system, we’re on a soundstage. We built a 120-foot long, 70-foot wide cave set and flooded it with five feet of water. We had one other set that was like 60-by-70 feet that had 15 feet of water. Between those two sets, I shot every cave. So we had 13 sets on two stages.
It was just about turning them over and being really creative. Alec Hammond, my production designer, is just a mad scientist. We figured out how to shoot every square foot of every rock and make it look like it’s a different cave just by using lighting tricks and key set-pieces that we would turn or rotate. It was really difficult. There are multiple scenes where they swim off the set and they just swim back onto the same set.
What were some of the biggest considerations for filming and lighting the underwater sequences?
The lighting was really challenging because you want it to feel dark, but it can’t be darkness, right? We wanted to use the headlamps to motivate light, but you couldn’t really use them because if you tilted them down or got them anywhere near the lens, the lens would just flare out. We did a lot of experimentation with the headlamps. James Kniest, my director of photography, is also very good at his job. We ended up building these custom headlamps where we can control the luminance. But also we could angle them. And we would often yell from monitor like, “Hey, Lana, two clicks up!” And the cast knew that meant tilt it up, two clicks. And if you really study the movie, most of the time their headlamps are not pointed anywhere useful. But you see the light glowing, and in your mind it kind of motivates a general fill — that allowed us to come in with movie lights and get an exposure. I do think it works. I mean, if you study it, it falls apart pretty quickly.
Ultimately, it was a digital system. It was much more about all the stuff that went around the cameras — the underwater housing, the HydroFlex, all those systems that we were using. That was another massive challenge with this film because I couldn’t use a dolly, couldn’t use a steadicam. I couldn’t even do handheld shots because when the camera is in water, even at water level, it has to be in the HydroFlex underwater housing. That weighs 120 pounds alone. You’re not doing a handheld shot, you got to use buoyancy to keep it up. I basically had to learn an entirely new cinematic language. I couldn’t use long lenses.
I brought in Pete McCaffrey, who’s this legendary New Zealand camera operator, and he was just on the technocrane all day everyday. That was the only way I could really get the camera in and do some more traditional moves. But even those are impossible because you can’t drop marks in the water! How do the actors know where to go?
In addition to getting to work with the local crew, what were some of the biggest benefits of filming in Thailand?
As far as the actual economic incentives, the cost of living is much lower over there. We got a lot more bang for our buck. At a certain point, the cost of living can price a movie out of an area. If you’re having to pay a certain wage so people can live in that area, the studios only want to invest a certain amount of money in a movie. You can’t just physically make the movie there. And so sometimes, I thought a little bit about, “Alright, well we’re paying less than we would elsewhere. How do I feel about that?” And it was explained to me that this was a film industry hungry for projects. These were outstanding wages given the cost of living in that area and they were thrilled to have the work. So that’s how I wrapped my head around it.
I really embraced Thailand as a character in the film and tried to make it feel like we couldn’t have shot the movie anywhere else. It wasn’t just about economic incentives or labor costs or equipment costs.
The industry is really excited right now about the success of films like “Obsession” and “Backrooms” from younger directors. What do you make of these conversations happening in horror spaces?
I mean, it’s just hard. It’s always going to be hard to get movies made. It’s not like Disney made “Obsession,” or Netflix made “Backrooms.” It’s not like major studios are embracing this kind of filmmaking. These are filmmakers that fought like hell to get their movies made, and I’m so happy that they’re enjoying this kind of success. I don’t think it’s going to make it any easier, though, to make movies. It might make it a little bit easier for Curry Barker to make his movie, obviously. But that’s the exception. That’s not the rule. I don’t think you’re going to see major studios chasing down young filmmakers who have had success with a couple YouTube shorts to make wide releases. Maybe I’m cynical, but I just don’t see that happening. I think it’s still going to be hard. It’s almost always going to be hard, and it’s hard for a reason because it tests you, and for that reason, only people who can really do it are able to keep doing it.
“The Devil’s Mouth” is now streaming on Prime Video.
This interview has been edited and condensed.
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