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 coming of age adventure story about a teenage boy, with some crime and romance thrown in, and some great West Texas scenery. And not only are there 4 different snake scenes (plus a rattlesnake tail cameo) but best of all, there's a science teacher who teaches his class about snakes used as weapons - my favorite snake movie cliche.
Clay Watkins is the teenager. He doesn't fit in at his rural Texas high school with his spiky hair, black eyeliner, and lip piercing. After he misses a shot at the buzzer that causes his team to lose a basketball game, some of the other boys in school start to bully him worse than they had been already, including the alpha bully Doug and his girlfriend Regina, who will play a significant role later.
In his classroom, Clay's high school science teacher pulls out a live snake (a boa constrictor) and starts spouting natural history information to his class. I had to write down his complete speech because it is a wonderfully weird combination of facts and crazy talk:
"I range from the high cloud forest to the dry lowlands. I am beautifully marked and only moderately arboreal. What am I? I am a Boa Constrictor. ...
Due to a generous supply of rodents and untethered pets, boas are frequently found near human habitats. They're primarily crepuscular."
He asks the class for a definition of "crepuscular" but nobody answers. He walks up to Clay and asks him for a definition of "crepuscular." Clay's head is down and he's not paying attention, so the teacher puts the boa's head close to Clay's face and asks again. When Clay looks up and sees the snake, the shock knocks him over backwards in his chair. The kids laugh at him, including Regina, and someone tells him to watch its fangs. The teacher tells Clay "You have just met a red-tailed boa. And no, it has no fangs."
Then he asks Clay "How have poisonous snakes have been used throughout history?" Clay doesn't respond so the teacher answers "Poisonous snakes have been used throughout history as weapons to kill. Placed in strategic locations at certain times they have been known to be quite effective. They've also been used as watchdogs or sentinels. You put one in your safe, no one's gonna steal the family jewels." Later in the movie Clay remembers this lecture and puts it to use.
This reminds me of the "snake put in a mailbox to kill someone" cliche. When most people talk about using a venomous snake as a watchdog, nobody ever seems to consider that snakes are living animals that need food, water, and air to breathe, and that their first response is usually to get away and hide. Put one in a safe and it will probably die before anyone tries to open it. If snakes aren't kept at their optimal temperature they can also go to sleep or even die. An inactive or dead snake or one that runs away and hides does not make a very good watchdog. You're better off using a real dog, though I don't recommend stuffing one into a mailbox.
After school, Clay is lured out of his truck when he hears Regina yelling for help, but that was just a ruse. He is grabbed by a bunch of boys including Doug who calls for a snake. Someone brings a large harmless albino corn snake or rat snake, a pet, not a snake that's native to west Texas. Doug puts the snake's head in Doug's face, then un-buckles Clay's belt and puts the snake down his pants. Some people might enjoy that, but not Clay who is angry and humiliated, but since he pulls the snake out himself, and sets it down on the ground, it doesn't seem that he is really afraid of snakes.
Clay is due in court the next morning, charged with driving over a mailbox but his grandfather, the county Sheriff, convinces Clay that he can talk the judge into dropping the charge if Clay takes his canoe to the Pecos River and spends a few days paddling down the river, as the Sheriff did when he was young. He warns him to beware of scorpions, centipedes, and snakes. The same night, the sheriff and his deputy set up a trap to stop their van and catch two drug dealers, but in the middle of the arrest someone crashes into the van and the men escape, stealing a passerby's car. Regina was asleep in the back seat of the car, so they kidnap her and head to the same place where Clay put in on the river.
A few days later, Regina is gathering firewood for the men when she falls down and calls out that she saw a snake. One of the men finds it and cuts its head off with a knife, showing it off proudly. He tells his partner that the snake will be lunch, which disgusts him.
The snake used in this scene is a real rattlesnake with its head cut off. It's either a western diamond-backed rattlesnake or a Mohave rattlesnake, both are native to the area.
After the bad guys steal Clay's canoe, he sneaks back to steal it, but he hears Regina screaming for help and remembers that his grandfather told him to always help people. He sets out that night to find weapons to help him overtake the two larger men, including one with a handgun. He also remembers the teacher's lecture about snakes used as weapons and his grandfather's mention of dangerous scorpions and centipedes and snakes, so he gathers up one of each. The next morning he plants them in strategic locations while the men are sleeping. After waking up, one man is stung by a scorpion hidden in his boot, the other by a centipede hidden in his canteen. The scorpion victim opens a bag to look for a first aid kit and a rattlesnake springs out of the bag like a jack-in-the-box and bites him on the cheek. We see a shot of the rattlesnake falling on the bag and see the man moaning that he's been bit and then we see him slumped over on the ground. The snake bit guy was not dead though, that takes a while. Later we see him lying at the edge of the river with a swolen face, and then finally we see him dead and floating in the river.
Clay uses the distraction to rescue Regina who, of course, falls for him as they paddle downriver and camp overnight and he feeds her cooked fish and roasted river rat.
rattlesnake used in this scene seems to be a western diamond-back. The snake that bites the man on the cheek is a fake snake, probably a hand-controlled puppet, but I'm certainly not going to blame the filmmakers or the actor for not using a real rattlesnake in the shot.