Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is the first sequel to Jurassic Park (1993), which also included a brief scene with a snake. People wanted a lot more dinosaur action in the sequel, so Spielberg gave it to them in this one. A few actors from the first movie return, mainly Ian Malcolm (Jeff Goldblum) who has the best lines. When some new guys get excited the first time they see giant living dinosaurs, Ian tells them not to get too excited because it starts with oohs and aahs but later there's running and screaming. Of course, that is exactly what the audience wants.
Jurassic Park was built on Isla Nublar off the west coast of Costa Rica, but about 80 miles away is Isla Sorna where the dinosaurs in the park were bred, and it still has intact populations of free-roaming dinosaurs. Four years after Jurassic Park was abandoned, John Hammond, the old rich guy from the first movie who created the park, sends a low impact team to Isla Sorna to observe and document the animals without the animals being aware of the humans. He wants the team to photograph the dinosaurs in their habitat to convince people that the island and the dinosaurs should be protected and kept off limits. Malcolm observes that he went from capitalist to naturalist in four years. But Hammond's plan goes bad in a hurry when a second unexpected well-equipped team is helicoptered to the island, led by Hammond's nephew Peter who just took over control of his company InGen. They start hunting and capturing dinosaurs to put in a new zoo Peter is building called Jurassic Park San Diego. (For a while it feels like we're watching a high-tech update of Hatari!, nooses and all, but without John Wayne.) Despite all the death and disaster that happens on Isla Sorna, Peter's team manages to bring an adult and a baby T-Rex to San Diego, but that's long after the snake scene.
At the very beginning of the movie we see a rich family lounging on a beach on Isla Sorna with a group of uniformed servants. (I'll bet that's what it's like when you sail on Spielberg's 300 foot yacht.) A young girl wants to walk down the beach but her mother is worried it's too dangerous. "What about snakes?" she asks her husband. He tells her there aren't any snakes on the beach and to let the girl go. But soon their daughter is mobbed and injured by very small dinosaurs called "Compys" and that's how the word gets out that there are dinosaurs on Isla Sorna. It also sets us up to think about snakes on the island and the dangers of little dinosaurs as well as the giant ones.
The Snake Scene
Sarah Harding (Julianne Moore) is part of Hammond's team. She's invloved in a brand new science - now that dinosaurs walk the earth again - Paleontological Behavior Study. In just a few days on the island she has learned that some dinosaurs pair bond and take care of their young, unlike most present-day reptiles, and that includes T-Rex. After a mom and pop T-Rex destroy both camps and all the communication equipment, both teams merge and hike off to find an old communications center to call for help. But the T-Rexes follow them and attack them one night. Everybody runs away screaming, as predicted. A few of them hide in a small concavity behind a waterfall where the T-Rex can't quite reach them except with its tongue. That's when the snake appears. Unless you're a speed reader, it will probably take you longer to read this sentence than the snake was visible in the movie. Earlier we observed a paleontologist named Dr. Robert Burke (Thomas F. Duffy) as part of the hunting team. He's a dinosaur know-it-all, but he apparently has a fear of snakes. When he is behind the falls, we see a red, black, and white-banded snake crawling into his jacket. He screams, as any of us would - "Oh my God! A snake! Help me!" then runs straight into the T-Rex's mouth, which quickly pulls him up the waterfall out of our view. We know he's dead when we see blood run down the waterfall. (That's the second time Spielberg used blood flowing in water in this movie to show that someone was dinosaur food. That's how you keep a PG-13 rating.)
You'd think that a wildlife expert, even one whose field of study involves extinct animals, would know he had a better chance of staying alive with a venomous snake down his shirt than he'd have against a gigantic carnivorous dinosaur, and he would not have run so quickly to his death. He should have known that there was a chance the snake would not bite him. I guess it's possible he knew the snake was venomous and felt it bite him. Then, rather than die an agonizing death as the venom slowly killed him, he chose the quicker, less painful death by dinosaur, but I doubt that. His motive doesn't really matter because he's one of the bad guys trying to capture dinosaurs, so we had to see him die a grisly death caused by one of his prey. Death by venomous snakebite would not have been sufficiently gruesome. There are more gruesome bad-guy deaths to come.
So where did the snake come from that it ended up on Dr. Burke's shoulder? Since when do snakes hang out in the saturated rocks found behind a waterfall? That's one of the most unlikely places to find a snake I've ever seen in a movie. From what I could see in the dark, water-streaked scene, there were no trees above him that the snake could have fallen from, and if there were, they'd be all wet, and most snakes don't stay in wet places very long. Maybe the snake fell on him in the forest when he was running and he didn't notice it until he was under the falls. That probably makes the most sense.
The snake used in the movie appears to be a Milk Snake, which is harmless, not venomous. (Some venomous coral snakes in the neotropics can look similar to North American Milk Snakes, with red bands touching the black bands, so the Milk Snake is perfect for the role.) Obviously, live harmless snakes must be used in a movie to portray live venomous snakes, which are too dangerous. (They don't shoot actors with real bullets, either.) I'd rather see a live harmless snake in a movie than a fake prop snake, or worse, a CGI snake, though it does promote the misconception that harmless snakes are dangerous.