Continuity mistake: Near the end when Karen is handcuffed to the banister, in one shot her hands are handcuffed but not to the banister. This is before Tom shoots the handcuffs to free Karen.
Continuity mistake: When Christian Slater is in jail, he wakes up to the sound of water. He than swings his legs into the water and stands up. If you look, his pant legs are already wet before he swings his legs off the cot.
Suggested correction: He waded through water when he got off the armored truck.
Continuity mistake: When we first see the horn on the dam it is a dark rusty brown color, but when the dam finally breaks it is a bright yellow.
Continuity mistake: Minnie Driver helps Christian Slater escape from the prison by unscrewing a metal cage. Right before she is finished unscrewing there is an underwater shot of the cage already broken through. Cut to the next shot and she frees the cage again.
Continuity mistake: When Tom hides the money at the bottom of the "Portman" crypt, the water has almost reached the name on the crypt. But later when Jim forces Tom to bring the money back up the level of water has barely risen any in the last few hours.
Continuity mistake: During the conversation while driving in the security truck, the amount of rain on the windshield changes significantly between the shots from inside and outside the truck.