Continuity mistake: When Harrison Ford is watching his wife laying in the bathtub ready to drown, the camera shoots her head several times between cutaways to Ford and the running water. Watch her head relative to the top of the tub in the various shots. In some her head is much higher than in others yet her body never moves.
Continuity mistake: When Claire is in the tub after her husband gives her a drug to immobilise her, watch her hair in various shots. It keeps changing position even though she is unable to move it out of the way with her hand.
Continuity mistake: Claire takes a basket of flowers over to the neighbor's house. Notice when she first goes to the side door the flowers take up most of the basket and are arranged a certain way. When she turns and is spooked by the car in the driveway, the flowers are arranged differently and do not take up as much of the basket.
Continuity mistake: In one scene when Michelle Pfeiffer is in the garage looking at the photo album, we see her looking at a picture of her daughter who is in a black vest. The camera angle then changes to one looking at her from across the room and we see her turn the page. We then see her half turn a page and the camera angle changes to over her shoulder to where we see her turn the rest of the page over, but if you look closely at the page before you can see it is the picture of her daughter in the black vest again.
Continuity mistake: When Michelle Pfeiffer is walking up to her door towards the middle-end of the movie, Michelle puts the key in the door to unlock the door, but she never unlocks it. Then the lady next door comes up and scares Michelle and when they go in, the door was never unlocked but somehow Michelle still got in.
Continuity mistake: When she is paralysed and drowning in the bath she tries to use her feet to remove the plug. Watch her big toenail closely, it varies in length, indicating they probably used a foot double.
Continuity mistake: When the bathtub is shown full, it is filled perfectly to the rim, which means the tub is level. When Claire is being drowned in the tub by Norman, the water is clearly deeper at one end of the tub, indicating that the tub is slanted.
Continuity mistake: When Claire gets the box and necklace out of the lake, she sees the necklace and lays it down on the open box. She goes to get the phone and then Norman quickly appears. She then later has the necklace on in the tub.
Continuity mistake: When Claire is in the bath, paralysed from the drug Norman gave her, and the water is rushing in, her head changes position: At first, her head is below the waterline, and then it is above the waterline - then Norman slips and hits his head - and then her mouth, nose and eyes are below the waterline.
Continuity mistake: The first time Michelle Pfeiffer sees the tub (approx 35 minutes in) full to the brim, she walks up to it and the camera angle is from the tub to her front. She rolls up her sleeve, then with the camera angle change to her back, she approaches the tub, and the sleeve is unrolled as seen in the reflection in the water. Then she rolls it up again.