When Matthew rapes Jennifer, his glasses have no lenses during a close up shot. This may be due to the director not wanting any sort of reflection showing up in the lenses during that shot. The lenses reappear afterwards.
Jennifer climbs into the boat toward the end of the film. She had been underwater, so her hair is wet. When she takes the boat in circles, her hair is dry.
When Matthew smears Jennifer's blood onto the knife, the pieces of paper behind him on the floor completely change between shots.
Johnny tosses Jennifer's swimsuit to his right, but in a jump cut it switches to his left.
When Jennifer hears Matthew knock at the door, while she puts her clothes away, the second drawer opens itself between shots.
After firing her gun at Johnny, Jennifer cocks the hammer. Her weapon is a semi-automatic pistol and the hammer should remain cocked after firing once.
When Jennifer uses the outboard engine to kill Stanley, he is too far away from the propeller to be injured by it.
As Jennifer is putting clothes away in the top left drawer she feels the pistol, removes the clothes and places them on top of the dresser. As she turns and walks away to answer Matthews knocking, the clothes have disappeared.
In the opening shot, as Jennifer gets into her car, people on the street, stop, stare and even point at the camera.
When Jennifer runs away in the woods and stops to throw the wooden tree trunk at the two men chasing her, a female crew member can be seen on the far left of the screen.
When the guys tow Jennifer's boat, shots from inside the speedboat show camera shadows on one man's legs.
There is a time window of barely two weeks between the rape and her revenge spree. That is not nearly enough time for her wounds to have healed so cleanly.
She would not have been able to continue living in the house without her attackers realising she was still there, considering it was such a small town. If nothing else, she would have had to re-stock on groceries.
When Jennifer begins writing her story, she says in her mind "Chapter 8," but types Chapter 9.