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 romantic comedy with a comic snakebite scene. It stars George Clooney as David Cotton and Julia Roberts as Georgia Cotton, a divorced couple who can't stand each other but have to try to get along when they fly to Bali for the wedding of their daughter Lily (Kaitlyn Dever). They are hoping to convince Lily to call off the wedding before she makes the same mistake they made 25 years ago, marrying someone she has only known for a month.
Georgia has a French boyfriend named Paul (Lucas Bravo) who also flies to Bali for the wedding. David convinces everybody to go on an outing to the the temple of Tanah Lot, which tradition says is cursed and will bring unhappiness to any unmarried couple that visits. David probably read about the curse in his guide book and hopes that the curse is real, at least in her fiancés mind, and will stop Lily's wedding, but what he didn't count on is that it would curse his ex-wife's relationship instead, giving David another chance with her, because in any romcom of this sort when two exes hate each other, they're destined to get back together. When Lily's fiancé Gede (Maxime Bouttier) tells her about the curse as they are walking towards the temple, she tells him that they don't have to go into it, even though "It would take a lot more than a curse to mess us up."He replies: "Maybe other couples aren't so lucky" and that sets us up for the snake bite scene.
Then we see Paul and Georgia walk into a cave that he tells her is called a snake cave. She is hungover and nauseous from a wild night of drinking with David and happy to be out of the heat. Then Paul drops down on one knee, holds up a ring, and proposes to Georgia. She is surprised and confused so she awkwardly tells him about her night with David, emphasizing that nothing happened between them. He says he doesn't mind, then starts slurring his words. She asks him why he's being so weird. He says he thinks something bit him. Then he looks down and chuckles when he sees a snake, and falls to the ground. She picks up his leg and finds the bite on his calf. He begs her to do something, so she sucks the wound and spits. She says she thinks she got most of it, realizing that she had snake venom in her mouth. Cut to everybody in a hospital room with the doctor telling them that he will have some numbness in his extremities but no lasting effects. We are probably seeing David after he's been treated with anti-venin. It's doubtful he would have survived as well otherwise.
Then the doctor tells Georgia "He's going to be fine but don't do that again" meaning that it's not a good idea to suck out snake venom, no matter how often we see it done in movies.
I don't know if the snake we see is real or CGI, but we see it moving through the water realistically. I suspect it's supposed to be a Yellow-lipped Sea Krait, a highly-venomous sea snake with black and white bands that is common around Bali, and a sea snake that also spends much of its time on land, which means its presence in the cave is believable. It's also believable, if unlikely, that it could have bitten Paul on the lower leg if Paul accidentally stepped on it or kneeled on it when he proposed.