Continuity mistake: The white cloth that Sarah presses against her cut and bleeding wrists never appears to have blood on it in any of the shots.
Continuity mistake: All through the climactic last quarter of the movie, Sarah's socks change from below to above the knee and back and forth constantly.
Continuity mistake: After Nancy slits Sarah's wrists, Sarah runs upstairs to her bathroom and grabs a cloth which she presses both of her wrists to. Eventually Sarah ends up lying on the floor on her back. The cloth is under her left wrist. In the very next shot the cloth is gone, and in the next shot the cloth is back.
Continuity mistake: When Nancy (pretending to be Sarah) and Chris are on the bed kissing, Sarah bursts in. First Nancy has no lipstick on then it shows Sarah and then back to Chris and Nancy and she has had her lipstick re-applied.
Continuity mistake: When Sarah and her Dad first enter their new house, it's pouring rain and the roof is leaking in a number of places, but the wooden floor has no puddles, only a few strategic but ineffective drips.
Continuity mistake: When Nancy, Bonnie, and Rochelle walk up to Sarah at the football field and invite her for coffee, Nancy is carrying a large black book with the spine out. The camera cuts to Sarah, and when it cuts back to Nancy, she is carrying the book flipped around with the spine in. (00:11:20)
Continuity mistake: When Sarah runs to hide in the school bathroom and slams the door shut, we see a gap between the door and the other side of the cubical wall, of about half an inch, enough to see Sarah. Yet when the shot zooms to the bolt sliding, there is no gap.
Other mistake: When Sarah is in the magic shop with the owner and they see the glamour of the shop front exploding, both womens' clothes and hair blow around with the force of the explosion. A glamour is a visual trick and as there was no real blast, their clothes/hair shouldn't have moved.
Audio problem: Nancy shouts, "Yay Chris! Go long! Go for the pass, baby!" at football practice, and her voice is so distorted that the viewer can easily tell the line was added post-production (with too much gain).
Continuity mistake: The entire time that Sarah is parked with Chris, it is nighttime with a completely black sky. However, while Sarah is running through the trees after being attacked by him, a bright blue and white sky can be seen all around her. It then returns to complete darkness when she reaches Rochelle's house. (01:01:55 - 01:04:00)
Continuity mistake: In the beach scene where it's revealed many dead sharks were washed ashore: one glaring mistake is obvious. The shark closest to them seems to be a great white or related species and his head is faced towards the beach. However, in the closeup, this creature suddenly becomes a sword fish or sawfish type with a defined snout that is now facing towards the ocean. Which is an opposite direction and a completely different creature in general from what the original wide shoot showed.
Continuity mistake: When the girls wake up on the beach, they see Nancy out in the surf, walking on water. As she casually strolls back to the shoreline, a wide shot shows the water is calm and flat and blue from the beach to as far as the eye can see. However, as the camera cuts to Nancy reaching the beach, the surf behind her is suddenly rough and crashing and murky brown, with 3-foot waves breaking on the shoreline.
Continuity mistake: During the showdown between Nancy and Sarah with the chest of drawers, the drawers slam flat against the wall in the alcove. In the next shot, the drawers have not only moved away from the wall, but also away from the alcove entirely; a considerable distance. (01:29:10)