Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a slow and tense independent movie that uses a snake used as a lethal weapon. The snake is the catalyst for the escalation of a violent family feud.
In rural Arkansas three men were abandoned when they were boys by their drunken father. He cleaned himself up and started another family and fathered four more boys. The three boys' mother teaches them to hate their four half brothers and a family feud heats up after the father dies.
After a few angry encounters between the two groups of men, we see one of the second family aim a rifle at a Cottonmouth crawling on the ground when his older brother stops him from shooting it because he wants to catch the snake. He doesn't say why he wants it. Then we find out that one of the three brothers' dog is dead, killed by a snake. We learn that a kid found the dog bitten on the nose by a snake that was curled up in the dog's water dish. Then he found the snake and cut its head off with a shovel. When a friend of the three brothers tells them that the snake was put there by one of the four brothers, the revenge violence and bloodshed begins.
While all of this is not impossible, it's extremely unlikely that it would work. We are asked to believe that you can put a venomous snake in a dog's water dish and it will stay there until the dog comes to the dish and gets bitten. While it's possible a dog would be curious enough to investigate the snake and unaware of the danger, there is no way a snake would just sit there in the bowl after being captured and hauled there in a sack. We're supposed to believe that, since it's a Cottonmouth which lives and feeds around water, it would prefer to stay in the water rather than quickly crawl away from there as fast as possible and seek shelter, which is exactly what would happen. The writer/director of this movie also wrote and directed the movie Mud, which also uses deadly Cottonmouths, but in a more dishonest way.
We don't see any of the snake encounters that happen after we see the snake crawling on the ground, we only hear people talk about them. The snake is never in the same shot with any of the actors. This makes sense because the snake we see is a real venomous Cottonmouth.