The scariest survival thriller of 2026 was filmed on sacred land deep in the Amazon

"Look at the giant snake movies that have come before us," Nelson tells Polygon. "With the exception of Anaconda, they're kind of jokes." (To be honest, even Anaconda is kind of a joke, to the point that Jack Black and Paul Rudd turned the concept into a meta-comedy in 2025. And that's coming from someone who loves Anaconda.)

Beware Boiúna couldn't be more different from Anaconda (both the 2025 spoof and the 1997 original). This is no adventure-horror romp with big stars like Jennifer Lopez and Ice Cube. Instead, Beware Boiúna is a grounded, gritty army crawl through the literal mud and muck of the Amazon as a truck-sized, mythological snake unleashes its fury on anyone who dares put its fragile ecosystem at risk. Spawn screenwriter Alan B. McElroy's script doesn't pull any punches — nobody is safe in this movie — and Nelson captures it all in brutal, unflinching detail.

To pull this off, Nelson, his crew, and a cast that includes Jessica Rothe and Logan Marshall-Green, had to trek deep into the rainforest and brave the elements (and lots of dangerous wildlife). For Polygon's 2026 Fall Preview, we connected with the director over Zoom to find out how he made the first great giant snake movie since 1997.

Filming in the Amazon

Beware Boiúna takes place in the Peruvian rainforest, but it was mostly filmed in the Colombian jungle. However, early on in the production process, the studio tried to figure out if there was a way to make a snake movie without actually transporting the entire crew deep into the Amazon. Nelson quickly pushed back.

"They started to look at how much it was gonna cost to shoot in all these different jungle areas around the world," he says. "I'm just thinking to myself, 'The movie takes place in the Amazon. We should shoot there.'"

Eventually, one of the film's producers, Jeremy Bolt, traveled to the Amazon to scope it out. Nelson followed soon afterward and was immediately convinced this was the only option.

"As soon as they started taking us around, showing us the boats, taking us down the actual Amazon River, showing us some of these jungle areas, I was just like, 'It has to be here, dude.'"

Surviving the Amazon

"The Amazon is not as unfriendly to film as one may think," Nelson says. "It's challenging, but the crew we had was incredible."

He adds that the film's conversationist message, in which the mythical snake Boiúna protects the Amazon from loggers and gold miners, helped win over the locals and got them access to parts of the jungle they otherwise never could have seen, let alone filmed a horror movie in.

"The elders who let us shoot on their land, and ultimately blessed us to be there were super cool."

As for the actual wildlife, the director says it's not quite as dangerous as movies like Anaconda suggest.

"Everybody hears that in the Amazon, everything wants to kill you," Nelson says. "I walked away with a very different mindset, which was: Sure, everything there could kill you, but it's not necessarily there just to kill you."

That said, the crew did hire a snake wrangler who served as general handler for all dangerous creatures and was later crowned the "MVP of the shoot." As they traveled through the jungle, the wrangler would walk about 10 steps ahead of the rest of the crew and look out for potential threats.

Even so, there were a few close calls.

"It was raining one day and there was a Brazilian wandering spider just on somebody's umbrella, just right there. That's not a good bite to have," Nelson says. (Indeed, Phoneutria nigriventer carries a venom that can cause intense pain, increased blood pressure, and prolonged erections in men — yes, really.)

"At one point, somebody did get bitten by a tarantula," Nelson adds, "but obviously that's not life-threatening."

Creating Boiúna

In Brazilian mythology, Boiúna is a large black snake with shapeshifting powers. The version in Beware Boiúna is a little different (it never changes form), but it is about the size of a truck. Nelson and his crew created the beast using a mix of practical and visual effects, with an emphasis on giving the cast something to react to during shooting, which in some scenes meant a "huge cardboard cutout of the head" for the cast to react to.

"I didn't want any tennis balls," he says. "I wanted to give them something to look at; give them something that they can feel moving behind them."

That doesn't mean they lugged some giant, animatronic deep into the jungle.

"When I say practical effects, it's in how we puppeted the environment," Nelson says. For example, in a lot of scenes, the team used a long piece of HVAC painted black to represent the snake. "We dragged it through the jungle and pulled it into water, to give a sense of something large and ominous that was next to them, that was moving, that they could hear, that they could feel."

Nelson and his team also found other ways to manipulate the environment and inject a bit more realism as well.

"We built full-on trees that were falling and crashing and sending debris up in the air," Nelson says. "We built this truss out in the middle of the jungle that could pull somebody 40 feet. In the trailer, when you see that guy get eaten, that's not a digital double. That's a real guy who gets yanked up into the air. We took a cannon full of debris and dirt and blew it out of those trees to represent the snake coming out."

Ultimately, it all works shockingly well. While you'll never quite forget you're watching a CGI monster swallowing up whole humans, every choice made behind the camera ensures Beware Boiúna feels as real as possible on the big screen. From the beautiful-but-deadly scenery to the cast's grounded performances, it all adds up to an impressively sturdy giant-snake horror movie. Maybe now the genre will finally get the credit it deserves.

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Beware Boiúna releases in theaters on Oct. 2.