‘Beware Boiúna’ Review – A Failed Creature Feature [Fantastic Fest 2026]

There is a very simple reason to be excited about Beware Boiúna: a gigantic mythical snake, roughly the length of a basketball court, hunting people in the Amazon rainforest. That is a creature-feature premise that should almost sell itself, as anyone who is a fan of horror and monster movies will surely be sold on this. Mike P. Nelson’s film follows a group of young doctors on a humanitarian mission along Brazil’s Curuçá River, where their journey goes horribly wrong after they encounter brothers Brennan (Logan Marshall-Green) and Shawn (Jackson Bews), whose reasons for being in the jungle are far less charitable. Before long, the survivors find themselves in the territory of Boiúna, an ancient serpent from Amazonian folklore that sees the humans as intruders. Beware Boiúna does have some brutal moments once the creature finally gets involved, but man, it takes far too long to get to that point.

The first 30 or 40 minutes are probably the biggest test of patience. The movie spends a lot of time introducing the humanitarian group, their relationships, the brothers, and the various conflicts surrounding their journey, but very little of it creates the kind of tension needed to carry a creature feature before the monster arrives. Boiúna is barely seen for most of the first hour, and even when the snake does appear, the movie often hides it in darkness. There is a difference between building anticipation and making the audience wonder when the actual movie is going to start, and Beware Boiúna occasionally crosses that line.

Once Boiúna begins attacking, things improve a little. The kills are expectantly brutal, and there is a viciousness to some of these attacks that gives the film the energy it desperately needs in the first half. The problem is that the attacks themselves are often too predictable, as the movie will establish exactly where the snake is going to strike, then spend enough time telegraphing the attack that there isn’t much left to surprise you when it finally happens.

That is very annoying because the movie has a fantastic monster at its disposal, and she is desperate to work. She is enormous, capable of moving through both the jungle and water, and is essentially an ancient territorial predator defending her home. That distinction is one of the more interesting things about the premise. A reminder that this creature isn’t hunting these people because she is evil or because she has some elaborate supernatural agenda. The humans have entered her territory, and she reacts accordingly, which in it of itself is a good building block. There is an opportunity here to make the jungle itself feel dangerous and unpredictable, but the film doesn’t consistently take advantage of it.

Kiana Madeira gives the movie a strong central presence as Lena, the boat mechanic who is tougher and more guarded than she initially appears. There is also more going on with her than the rest of the group realizes because she has a mission of her own. Madeira handles the physical side of the role well, and Lena becomes more compelling as the situation gets worse. Still, the screenplay doesn’t develop her secret mission or the other human conflicts enough to make them as interesting as the creature itself. When Boiúna is absent, I kept waiting for the movie to return to the thing I actually wanted to see.

Jessica Rothe plays Alli, one of the American members of the humanitarian group, and she brings some recognizable personality to the ensemble. Logan Marshall-Green also has fun material as Brennan Malloy, one of the brothers the group encounters. Brennan provides a human threat alongside the snake, which should create an interesting conflict over who the survivors should be more afraid of. Instead, that storyline mostly adds another layer of drama to a movie that already has trouble balancing its characters with its monster.

The CGI is another major problem here. Boiúna’s size is impressive in theory, but the visual effects don’t always sell the creature’s physical presence. Her first major appearance is particularly underwhelming, and the lack of practical creature work means there isn’t always a convincing sense of weight or texture when she interacts with the environment. The nighttime sequences make things even harder. The movie is so dark in places that it becomes difficult to understand exactly what is happening, which is especially unfortunate during action scenes that should be showcasing the snake.

That darkness also works against the suspense. A creature feature needs to control what the audience sees, but hiding the monster and making the action difficult to follow aren’t the same thing. Beware Boiúna sometimes seems to think that darkness automatically makes Boiúna scarier. It doesn’t. The best moments come when we can actually understand the physical danger facing the characters and watch them try to figure out how to survive it.

The movie also takes itself surprisingly seriously considering how wonderfully ridiculous its central concept is. There is nothing inherently wrong with playing a creature feature straight, and the film’s folklore elements could have supported a more serious approach. But there is almost no humor or self-awareness to balance the heavier material. A giant Amazonian serpent the size of a basketball court should at least allow for some moments of fun. Instead, this horror outing treats every situation with such seriousness that it occasionally feels like it has forgotten the basic appeal of its own premise.

That seriousness wouldn’t be an issue if the human story were strong enough to compensate. It isn’t. The humanitarian mission gives the movie an appropriate setting, and the conflict between the different groups creates some opportunities for drama, but the characters don’t have enough depth to make the long stretches without Boiúna particularly engaging. There are hints of interesting ideas about outsiders entering unfamiliar territory and the consequences of disturbing an ecosystem, but the screenplay mostly uses those ideas to get people from one encounter to the next.

The result is a movie that becomes much more enjoyable whenever it remembers what it is. The premise is terrific for the most part, as it promises an almost B-movie creature feature with the potential to have a new classic creature. The problem is that the movie spends too much time away from those strengths. The first half moves slowly and the scares rarely land as intended and when you mix that with inconsistent CGI, well it can be a pretty nauseating experience. Again, it has the ingredients for a memorable creature feature, but too often it seems afraid to have fun with them. When Boiúna is actually hunting people, the movie finally finds some of the excitement promised by its premise. When the characters are simply talking, walking through the jungle, or dealing with conflicts that never become especially compelling, the energy disappears again. 

Beware Boiúna had its World Premiere at Fantastic Fest 2026. The film will debut in theaters on October 2, 2026, courtesy of Lionsgate. 

Director: Mike P. Nelson

Writer: Alan McElroy

Rated: R

Runtime: 104m

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