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 family movie made for kids. It's full of forced family drama that makes up most of the plot, but I will happily ignore all that. The movie is loosely based on the real lives of the three Stouffer brothers, who all went on to become wildlife documentary filmmakers. The best-known of them is Marty Stouffer, whose TV show "Wild America" was an excellent portrayal of North American wildlife (and made him rich.) Rather than being a biographical story, the movie is more of a parody of wildlife filmmaking, turning it into a series of adventures. Filming wildlife takes an incredible amount of preparation and effort and time, much of it spent waiting for something to happen, but in this movie the boys just randomly turn on their camera and we're supposed to believe they are getting great footage, based on the film we see at the end.
The movie doesn't even try to pretend that some of the animal scenes are realistic - there are obviously fake animals and implausible situations. In a movie about a wildlife filmmaker who is striving for realism, I have to think that the filmmakers were having fun with the genre. There was no way they could get the kinds of realistic footage Marty Stouffer got, so they made it fake and funny instead. The Stouffer brothers must have been OK with this, because they have a cameo scene as the three mean-looking guys who steal everything from the boys' car.
In 1967 the three boys have already made lots of films, mostly daredevil stuff like you'd see in the old Jackass TV series. They buy a professional movie camera then leave Arkansas and drive around America looking for wild animals to film. They plan to sell the footage and get rich.
The Snake Scene
The boys drive to Wyoming to a mountain peak 8,734 feet in elevation to look for a cave full of hibernating bears. They secretly follow a woman to the cave and go inside. There is a lot of snow on the ground outside, so it must be freezing, but a short distance inside the very large cave, they see lots of snakes lying on the floor. Marty announces that they're Timber rattlers, drawn in by the heat. (True Timber Rattlesnakes are not found in Wyoming, but the name is a common one for any rattlesnake found in the woods, so I'll excuse them for that. And snakes do overwinter together in dens, so that's not entirely unbelievable, even though they wouldn't be found in a pile on the floor of a giant cave.) The snakes are blocking the way to the bear cave and the boys are afraid to walk through them, so Marty devises a plan to get snow from outside the cave and cover the snakes with it. (That might actually work. Some snake photographers will put a nervous snake in a cooler full of ice to slow it down so it can be posed. That's where the phrase "chill out" comes from. Maybe. I just made that up.)
As the boys walk over the snakes and the snow we see several rattles sticking up out of the snow shaking, as we hear rattling sounds. One of the snakes pops up out of the snow between the youngest boy Marshall's legs and he screams, then he jumps straight up after the snake strikes up at him. Marty chastizes him for screaming, which could wake the bears and kill them all.
Sure enough, once they get past the snakes, they find a group of bears sleeping in a large open area in the cave, and they wake them up. The bears attack the boys, and as they run towards the exit they see the snakes again and stop, because all the snow has melted. In fear for their lives, figuring their chances are better with the snakes than with the bears chasing them, they run through the rattlesnakes as we hear all sorts of rattling sounds and the snapping sounds of the snakes striking at them. They don't get bitten, and even more surprising, the bears don't keep coming after them.
The snakes we see in the movie are a mixture of real live rattlesnakes and obviously fake plastic snakes. One of the fake snakes strikes up when someone pulls on a line connected to it. The large rattlesnake we see is a Western Diamond-backed Rattlesnake, which is not found in Wyoming, and I think there are another couple of juvenile diamondbacks in the shots we see. The tails sticking up out of the snow, and the snake that strikes at Marshall are all mechanical contraptions.
The Alligator Scene
The boys go in search of alligators to film. They rent a boat at Stango's Alligator Hell and Stango guarantees that they will see gators. They boat into the swamp at night and Mark throws a bag of "bait" to attact an alligator, but the bait gets hung up on a branch. He gets out to wade to the bait to put it in the water when an alligator slids into the water. Marshall jumps in and wades out to help Mark. Mark gets back to the boat but Marshall drops his flashlight and swims down to get it. As the alligator comes at him, he throws the flashlight in its mouth to distract it, then swims to the boat. Just as he is getting into the boat the alligator rises out of the water and snaps at his feet, returning the flashlight to him. In the end all the boys get away safely.
The return to Stango's house, where he tells them a tall tale about a man named Phil who came to get a pair of gator skin boots, but ended up getting a whole gator skin suit. We see a stuffed gator on a wall with Phil's legs sticking out of its mouth.