Continuity mistake: As Rachel is preparing the peanut butter and jelly sandwiches, she places the knife on top of the open PB jar in a closeup, but in the very next shot the knife has disappeared, then reappears again. (01:23:15)
Visible crew/equipment: When Rachel pulls up to the crime scene where Jake was killed, as she gets out of the car you can see a grid of set lights reflected in the car window door. (00:12:30)
Continuity mistake: When Rachel is talking to Aidan at dinner, the position of her hair changes a few times. In one shot she pushes her hair behind her right ear, yet in the next shot her hair is pushed behind her left ear instead. (00:09:50)
Continuity mistake: During the scene where Rachel puts Aidan into the bathtub at Max's house, he is wearing very light white boxer underwear as he is being put into the water. A little while later when Rachel pulls Aidan out of the bathwater, he is suddenly wearing very dark blue/navy colored boxers. Although water would darken the color somewhat, this is far too dramatic a change to be natural. The lighter color couldn't have possibly darkened to that extent. They are two different pairs of boxers. (00:41:55 - 00:48:10)
Continuity mistake: When Rachel is trying to get Emily to speak to her at the police station, near the end of her attempt the shots alternate from closeups to wider views. In the closeups, Emily's hair is very messy and tangled but in wider views it is much neater and straightened. (00:16:35)
Continuity mistake: When Rachel begins to brake her car after seeing the deer on the road, as the shots keep changing the markings on the road also keep changing. In overhead shots the markings are a single broken yellow line, but in closeups of the wheels, the markings are solid double yellow lines. (00:30:40)
Continuity mistake: When Rachel pulls up to the old Morgan house she parks her vehicle on the gravel drive, angled into some tall grass. Yet when she leaves the house with the book, the vehicle is now parked halfway on the main road and is no longer angled (but is now much straighter) and is not facing any tall grass. (00:55:35 - 01:01:50)
Continuity mistake: As Rachel is trying to get Aidan to get in the bath at Max's house, she removes the blue towel from him and throws it on the towel- rack. Then during the rest of the bathroom scene, everytime we see the blue towel in shot it is in a different position each time. (00:39:55 - 00:46:35)
Continuity mistake: When Rachel is tucking Aidan into the bed at Max's house she puts a red blanket on him and then a brown blanket on top. Then during the next shots the red blanket goes from slightly visible to completely covered by the brown one and back again to being slightly visible. (00:39:15)
Continuity mistake: When Rachel finds Aidan standing at his bedroom wall and the image of a tree begins to burn in the wallpaper, she runs over and tries to pull him away. As she does this, the globe sitting on the desk beside them rotates itself between shots. (00:35:45)
Continuity mistake: When Rachel sits next to Aidan as he is in the hospital bed unconscious, as the shots change, the amount and position of the wires next to his head (to his right) keeps on changing. (00:50:35)
Continuity mistake: After Aidan comes downstairs and sits at the table for dinner, he is flicking through his photography folder. In the shot when Rachel walks away from him and goes back to the oven, there is no plate at Aidan's placemat, yet it is there in every other shot before and after. His drink also moves without him touching it. (00:09:05)
Answer: I was wondering the same thing. My guess is that it was when the water encircles his feet.