If you've read the Jurassic Park novel, then you're probably well aware that the Steven Spielberg-directed blockbuster leaves out quite a bit from Michael Crichton's original book, including a key sequence that involves the fan-favorite Tyrannosaurus chasing Alan Grant and the kids down a jungle river.
There are mild spoilers to follow, but in the novel, there comes a point near the end where Alan Grant, Tim, and Lex all have to sneak past a sleeping T-Rex and make their way down a river. In the time it takes Grant to successfully inflate a nearby life raft, the T-Rex awakens and begins to chase him and the children down a turbulent river where they do their best to escape with their lives intact.
While the storyboards have been available online since at least 2017, it's remained somewhat of a mystery as to what ultimately led to the scene being nixed, although many have more or less correctly assumed it was due to cost and the logistics behind actually realizing the massive sequence.
Speaking with CinemaBlend, the film's co-writer David Koepp (Spider-Man; Mission: Impossible) revealed how quickly Spielberg actually decided against even attempting to film the sequence and it sounds like there wasn't much of a debate as the ace director almost immediately said no.
"I think when I got there he was showing me a bunch of boards he’d done. Some of which were more or less exactly as you see them in the movie. There was a sequence with the river and the Rex and the kids. But he thumbs past it and said ‘Oh we’re not gonna do this.’ It was cut very early on. There was so much that was going to be challenging and difficult, and had yet to be figured out technologically in that movie. That the idea of adding water to that made Mr. Jaws… it was gonna be hard enough."
Considering the difficulties he faced filming Jaws nearly two decades prior combined with the already immense task of bringing realistic dinosaurs to the big screen, it's understandable that the 3x Academy Award-winner didn't want to add another incredibly difficult task to his to-do list.
While it would've only enhanced an already epic film, the scene will now go down in history as one of the franchise's greatest what-ifs, however, with Jurassic World: Dominion just around the corner and more sequels expected down the line, there's always a possibility someone could resurrect the concept for a future film.