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)
Revealing mistake: When Ellie is running to the shed, the same clip of her jumping a tree is seen.
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.
Character mistake: Grant and Tim could simply have moved to the side of the tree instead of climbing down with the Jeep right behind them.
Visible crew/equipment: When Dr. Grant discovers the eggs in the wild, the camera comes down a tad bit too far. The operator obviously notices because the shadow of the camera creeps in along with the shadow of wires attached to it. To correct this, the shot pans up a bit.
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)
Revealing mistake: The two Jeeps running during the tour are supposed to be automatically moving along the track in the road but several shots reveal there is nothing connecting the Jeeps to the track.
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