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 big dumb billion-dollar blockbuster movie that's a lot of fun. It's based on a 1995 movie that was based on a 1981 children's book. But this time, instead of a board game called Jumanji, it's about a video game, so all the characters in the game are in-game Avatars who can die and come back to life three times. And there are two nice long snake scenes to enjoy.
Basically, four high school student stereotypes on detention find an old video game named Jumanji. As they start to play, they get sucked into the game and become four video game stereotypes. Inside the game the smart unattractive kids get to be the good-looking heroes (Karen Gillan and Dwayne Johnson) while the dumb attractive kids get to be smart but not as good-looking characters (Kevin Hart and Jack Black.)
In the first snake scene, the four characters are searching for a clue in an exotic bazaar full of the kind of strangely-costumed people you only see in movies. (In real life they'd be wearing fake American T-shirts and flip flops.) A non-player character boy brings them to a room with a large closed basket and tells them a riddle: "What you need is in the basket. One false move, you're in a casket." They figure out immediately that there's a snake in the basket along with the clue they're looking for. Johnson is chosen to open it since he's the heroic player character. He opens the lid and a large snake rises up out of the basket. Everybody freaks out and Hart, a zoologist in the game, screams that it's a Black Mamba along with other information he didn't know he knew. Johnson frantically closes the snake back in the basket.
Next they decide that the clues tell them they should sit and stare at the snake so it will freeze and they can grab the clue. Johnson agrees, spewing some predictably stupid summer camp nonsense he learned about how you have to freeze when you see a rattlesnake. Jack Black is chosen to stare the snake down but when the lid is opened the snake bursts 20 feet out of the basket fangs first towards Gillan's face. Of course, just in time, superhero Johnson grabs it by the throat just before it gets to Gillan's face. Hart tells them they need to defang the snake, and then he gives a demonstration of how to snap a venomous snake's fangs out of its head. Please don't try this at home. Or anywhere. You will die! Seriously. Why do screenwriters keep writing this kind of stupid s**t !
The snake is not a real black mamba, it's a lousy CGI monstrosity, so don't look at it too closely.
In the next snake scene, as the four characters are close to finishing their task of returning a stolen jewel, we are asked to believe that Hart accidentally tosses the jewel about 50 yards up a hill. (You need to suspend a lot of disbelief to accept anything in this movie.) Gillan runs and does a flying somersault to retrieve it, landing right in the middle of thousands of snakes just lying on the ground. (They're CGI and they look bad but they look a lot better than the CGI jaguars we see in the movie.) Gillan crouches down and carefully works her way through the snakes over to the jewel, picks it up, then stands up. As soon as the snakes see sexy Gillan in the skimpy Lara Croft-like outfit she has been forced to wear in the game, they become erect. (Remember, adolescent boys are the target audience for these games.) Actually, the snakes are controlled by the main villain in the movie who we hardly see at all, Van Pelt, the evil explorer who stole the jewel and has the power to control animals, who shows up here. He tells Gillan that it's "game over" but she uses a great snakebite-based strategy to get out of danger.
We learned earlier that each Avatar has powers and weaknesses. Gillan's powers are various types of martial arts and her weakness is venom. We also learned earlier that characters have three lives, and we have seen that, when they die, they immediately fall from the sky and return they were, but with one less life available. Gillan tells Van Pelt that her weakness is venom, then stomps on a snake with her boot and the snake bites her on her leg above the knee. This, of course, explains why she had to wear those tight shorts throughout the movie. She smirks, then explodes into a cloud of blood. She falls from the sky a moment later with the jewel but outside the reach of Van Pelt or the snakes. Why did she get to keep the jewel when she died and returned? Keep suspending that disbelief. It's just a video game, after all.