With “Beware Boiúna”, director Mike P. Nelson delivers some of the most pure genre fun I’ve had at a movie theater this year. Together with screenwriter Alen B. McElroy, the duo fashions a wildly entertaining mix of nail-biting survival horror and old-fashioned creature-feature. The film’s unabashed B-movie energy combined with an enthusiastic self-awareness makes “Beware Boiúna” a genre lovers delight.

At the same time, “Beware Boiúna” doesn’t just blindly follow some genre movie blueprint. It packs several of its own surprises, most notably its deliberate, slow-simmering first half that sets the table for the terror to come. Nelson puts time into introducing his characters, defining their relationships, and building the tensions that move the story to where it needs to be. And while doing so, he keeps his slithering star in the shadows, waiting for the inevitable reveal that delivers the payoff audiences are looking for.

The story is set along the Curuçá River deep in the Amazon rainforest. That’s where Dr. Miguel (Juan Pablo Shuk) and two medical students, Alli (Jessica Rothe) and Callum (Will Close), are on a humanitarian medical mission. Their plan is to travel by riverboat to several remote villages where they will offer medicine and treatment to the locals. Escorting them is the boat’s captain, Raul (Jaime Newball) and his mechanic/deckhand Lena (Kiana Madeira), who has her own secret reason for making the trip.

The team arrive at their first destination, and after some initial hesitation, the villagers welcome them. But they’re soon joined by another boat full of suspicious men posing as land surveyors. They’re led by the creepy and cocky Brennan (Logan Marshall-Green) who immediately makes Alli and Lena uncomfortable. Things escalate after Brennan’s drunken brother Shawn (Jackson Bews) forces himself on Alli. She fights back with the help of Lena, but things don’t quite go as planned.

Little do the two parties know, their conflict awakens a colossal-sized creature from deep in the jungle – a giant snake the locals call “Boiúna”. Legend says “When there’s balance, she rests. When there’s imbalance, she defends.” And once Boiuna is disturbed, “she decides who lives and dies.” In a snap, the friction between the medical team and Brennan’s surveyors turns into a collective fight for survival as Boiuna begins hunting down the disruptive trespassers.

From there “Beware Boiúna” turns into a full-blown creature feature, with the tension cranked up to 11 and with no shortage of blood-soaked kills. The film works so well largely due to the immersive setting and some rock-solid effects. It was filmed on location in Columbia which vividly brings to life the many facets of the river and jungle. The effects are a crafty blend of killer practical work and strategic digital rendering. The lone visual misstep is Nelson’s occasional over-reliance on shaky-cams and quick cuts which at times can be more disorienting than exciting.

Still, I left the theater with a big satisfied smile on my face. “Beware Boiúna” is an entertaining throwback through and through, from its clear genre affections to its retro style of filmmaking. For old-school fans like me, it’s hard not to notice and appreciate the movie’s 1970s grit, seasoned with dashes of classic exploitation. Yes, Nelson takes his time getting to where he’s going. But we’re never bored. And the gnarly payoff makes it well worth the wait.

VERDICT – 4 STARS