Continuity mistake: Tim is trying to remember the Gallimimus, and we see a shot of him from behind with both arms down. In the opposite shot his right arm is up as he guesses the name.
Continuity mistake: When Hammond meets Grant and Sattler in the trailer he dries the glass with a white tea towel in his hands. A shot later it's pink. (00:11:32)
Continuity mistake: When Dogson talks to Nedry about the bribe, Nedry's hand on the suitcase changes in every shot.
Continuity mistake: When the movie begins a worker on the top part of the crate falls to the ground, face down. A split second later he's facing upwards.
Continuity mistake: When Grant covers Lex's mouth the dinosaur's breath blows his hat away. A shot later it's by his nape.
Continuity mistake: When Grant sees the first dinosaur, Malcolm is right behind him looking as well. The next shot is above Grant as he stands up. Malcolm has moved forward between cuts.
Continuity mistake: Muldoon lifts his gun to sight the raptor, in the next shot, he is raising the gun up and sights the raptor again.
Continuity mistake: When the gas jeeps stop for the first time they are in sunlight away from trees. At the end of the scene they are in the shade by some trees, despite them not moving in the scene. If you watch closely when Hammond tells them to stop they are in a massive patch of sunlight as shown with Dr Grant standing up. (00:21:05)
Continuity mistake: When the T-Rex turns the upside-down car around 180°, the car's tail lights move from right to left. When Alan and Lex try to move out of the way, the tail lights are moving from right to left again.
Continuity mistake: When the Dilophosaur spits on Nedry the second time, it is only on his forehead and eyes. In the next shot, a second later, it is all over his face and cheeks. It was too soon for the rain to have washed it down that far.
Continuity mistake: After the kids greet their Grandpa there's a shot outside of them waiting for the cars. The boy stands ahead of the girl, who's a meter behind. A shot later he has moved 5 meters behind.
Continuity mistake: The first time the cars arrive the girl walks to the rear passenger window and peeks inside. In the close-up she is meters behind repeating all of the movements.
Continuity mistake: In the tree, before Lex tries to feed the dinosaur there are no branches or leaves in front of her. She leans forward and a shot later a branch filled with leaves has magically appeared by her waist in a mere nanosecond. This keeps changing back and forth depending on the angle.
Continuity mistake: When Grant is feeding a dinosaur in the morning he is either holding the food with one hand or two depending on the shot.
Continuity mistake: When the kids and Grant wake up in the tree Alex covers her ears, but a shot later her arms are down by her side.
Continuity mistake: When the baby dinosaur is born, Grant's arm swaps from bent to extended between shots. (00:00:25)
Continuity mistake: When Grant and the kids wake up in the tree and Grant feeds branches to the dinosaur, Tim's position is an absolute chaos: He is either seated or standing; close to the dinosaur's nose or chin; far away or very close. There's no continuity whatsoever.
Continuity mistake: After Hammond says "Welcome to Jurassic Park" Grant is facing the jeeps, 3 meters away, with Ellie 5 meters to his right and Hammond 3 meters to his left. Grant then turns his waist around to the left, though his legs still face the jeeps. In the wide angle everyone has changed positions drastically: Grant's legs have magically turned 180° and Hammond is not only opposite Ellie but very close to her.
Continuity mistake: After Hammond says "Welcome to Jurassic Park" Alan is sitting on the floor with Ellie comforting him. A shot later she's gone, only to reappear 5 metres away in the next shot.
Continuity mistake: Ian gets out of the car to distract the dinosaur. Inside the car, he's nice and dry, but the second he gets out of the car, he looks like he's stood in a bathroom shower for ten minutes.
Chosen answer: They all left on the same boat Nedry was trying to get on with the embryos. You can hear Samuel L Jackson's character announce that the boat will be leaving at a specific time and everyone had to be there or be left behind.
Shannon Jackson