
Continuity mistake: After the T. Rex rolls Explorer 4 upside-down with Lex and Tim inside, in the closeup when the dinosaur bites on the rubber tire we see the hub hole at the center of the wheel rim, but two shots later the wheel cover is back on the wheel.
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