When Ben is talking to Julia Roberts' character outside the library after her first day of work, he is wearing a blue shirt and gray jacket. When he turns to walk away at the end of the scene, a white price tag is visible stick above the collar of the jacket.
While on the ferris wheel, they lean forward as their carriage goes by the ride operator. Leaning forward is listed as one of the most dangerous things passengers can do because of the lack of seat belts. Any ride operator working on the ferris wheel at any park, fair, or carnival are supposed to tell the passengers to stop leaning forward.
When Laura emerges from the sea after her feigned drowning, both she and her hair are soaking wet. However, as she runs towards the beach house her hair is almost dry and flowing behind her. When she enters the beach house, her hair switches back to being wet and straggly.
The cut/bruise on Laura's head comes and goes. After she is hit by Martin leaving a nasty abrasion on the left side of her forehead, he leaves to go to town after telling her they will sail that night. She goes outside to break the lantern, and the wind blows her hair off her forehead - no bruise. Later that night, she has her hair back in a braid, before they get on the boat - no bruise. Then, when she meets Ben a couple days later, she flips her hair off to one side and he sees the bruise. The very next day (or soon after) she has her hair back again with Ben, no bruise.
When Laura is on the bus to Iowa, a woman on the bus offers her a green apple.
The woman is eating one as well. The apple that the woman is eating goes from barely eaten to almost completely gone from scene to scene.
As Laura takes a bath after the carnival with Ben, she runs her hand through her hair and messes it up. Then she sees the straightened towels,stands up sharply, leaves the bathroom quickly and her hair is smooth and neat again.
In the opening scene, we see Laura standing in the water looking out over the ocean. She steps forward and the cuffs of her pants become soaking wet. In the next shot, the cuffs of her pants are dry again.
When a disguised Laura is visiting her mother in the nursing home and is in the closed bathroom getting a glass of water for her mother to take her pills, Martin opens her mother's door from the hallway, and the door opens to the left. When Martin returns later that evening, the door handle is clearly on the opposite side and the door now opens to the right.
While Laura is on the bus to Iowa, you can see she has perfect makeup on. She also has no sign of salt on her skin. Given that she has just swam through salt water and fled for her life , neither one is likely.
When Laura is in the bathtub after the carnival, she runs her hand through her wet hair and messes it up. She looks over, sees the straightened towel and stands up and puts on her robe. The next moment her hair is perfectly slicked back and combed neatly. As she walks down the hall to check the rooms, her hair goes back and forth from neat to messy.
When Laura escapes in the yacht, two crew members can be seen in the area below deck. There are no crew members visible in the area below deck. There are several moving and hanging objects that give the illusion that there are 2 people below deck.
When Laura comes home from the picnic with Ben, she switches on some music and there are several cassette tapes cluttering around the stereo. When she runs downstairs a few minutes later and hears the music start again, the tapes are gone. This is because the stereo was originally sitting on top of a table or desk, and when she runs downstairs later it has been set (by Martin, off-screen) on the floor against the door.
When Laura first goes over to Ben's house for dinner, Laura makes the comment that she likes Classical Music, and then elaborates, saying anything except Berlioz. Berlioz is a Romantic Composer. However, the term "Classical" is commonly used by the general public to refer to instrumental or orchestral music regardless of the time period in which it was actually created.
When Martin goes to take a drink at the water fountain (after a disguised Laura drinks), it sprays into his face. It is obvious that the squirt of water came from a separate source, not from the water fountain spigot.
The goof item below may give away important plot points.
When Laura shoots her ex-husband, she fires three rounds into him,the third finally flooring him. The gun clearly shows that the are rounds left in the clip (magazine) because as with All automatic pistols the slide is closed. However when Martin picks the gun up to shoot Laura it clicks indicating that it is empty. This is incorrect as with all weapons of that type, the slide stays back after the final round is fired - clearly showing an empty gun.