Continuity mistake: George Loomis tries to steal the boat and pulls the ignition wires straight out from under the lock. No one touches them but the next time we see them they're hanging differently. (01:14:55 - 01:16:10)
Continuity mistake: As George Loomis tries to steal the boat there's an ice bucket underneath the table to the right of the steering wheel. Later Polly comes back with some beer and grabs for the ice bucket, which has been rotated 45 degrees even though no one went near it. (01:15:35)
Continuity mistake: The gash on Lomas' head changes between scenes. (01:16:15)
Continuity mistake: The boat keeper throws his newspaper onto the ground as he runs to the boat that George Loomis is stealing. Later when Ray Cutler runs past that spot the newspaper is now on the chair. (01:16:25 - 01:17:15)
Continuity mistake: George Loomis gets the engine of the Myra III running then proceeds to untie the two ropes from the dock leaving them dangling off the side of it. In the next shot as the boat sails away we see no ropes. (01:16:30)
Continuity mistake: Inspector Starkey gets into the police car before Ray Cutler, who sits in the rear driver side seat as they pull away. Several shots later we see them again in a close-up chasing George Loomis and their positions in the rear of the police car have reversed. (01:20:50)
Continuity mistake: As Polly and George Loomis are rushing down the middle of the Niagara River a tree appears above Polly's head on the back of the boat. (01:23:10)
Continuity mistake: George Loomis goes over the falls and Polly is safely on an island in the middle of the river with green trees on it. Several shots later the trees are purple. (01:26:35)
Continuity mistake: Polly is safely on an island in the middle of the river as we see the helicopter coming to rescue her. Unfortunately when we see her they're showing us the falls from the wrong direction and we can see the island she's supposed to be on behind her. (01:26:35)
