Factual error: When Christian Slater and Minnie Driver are trying to get out of the water before it reaches the transformer, there is a real big problem with this scene. If there really was a flood and it was rising that high, the city should have shut off the electricity to the entire city, to prevent any electric hazards that may happen in that situation.
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.
Audio problem: When Jim has been pushed out of the boat by Sheriff in the church, his voice is heard echoing "no" at exactly the same time that he is spitting water out visually.
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.
Factual error: Current flows in a circuit. The guy on the metal antenna tower is similar to a bird sitting on a power line. No current flows through the bird. Furthermore, current would flow from the transformer through the water to ground. There would be no current flow up the metal antenna tower.
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.
Character mistake: Just after the shootout between the robbers and the armored truck drivers at the dip in the road, the teacher that is with the robbers pumps the shotgun about 3 times, without firing a shot after they crossed the water. This would just waste a perfectly good cartridge, since they hadn't been shot yet.
Factual error: In the scene inside Karen's house, the water level rises way too fast. The house is not in an isolated pool of water, but connected to the entire city. So for the water level to rise several meters inside the house would mean that the water rose several meters in the entire city. And that could not happen that fast. If it was a wave from the lake, the water level would drop again.
