Factual errors: The boat in the film for which they could not find the keys was a newer model Ski Nautique. These particular boats DO NOT use keys. They use a four digit start code which you must input into the key-less ignition panel. You can in fact see this panel in one of the first shots of the boat which shows the dash. It is marked by a big red START button.
Incorrectly regarded as goofs: Usually microwave ovens don't work while the door is open, as depicted at the end of this movie, however earlier on in the film it is stated that the microwave is broken.
Revealing mistakes: The lamp on the outside of the guest house (8 minutes into the movie) is mounted upside down.
Revealing mistakes: When Mari is unconscious, John tries to open her mouth and find out whether she's alive or not. You can clearly see Mari opening her mouth wider as John's hands move away from Mari.
Continuity: When Emma offers wine to Francis she has ONE bottle from which she fills both their glasses. Interestingly Francis has red wine in his glass and she has white wine.
Continuity: When Sara is leaving to see Paige her mother Monica stands up and tells her bye holding the paper she was reading against her side after Sara tells her bye she is walking to the vehicle (from a zoomed out shot) you can see that Monica is standing on the porch with her hand on her hip and the paper is no longer in sight.
Continuity: The location of the first stabbing on Paige's stomach changes before and after she is stabbed second time.
Incorrectly regarded as goofs: When the electricity is blown out, Emma is seen stirring the pot on the stove. The stove would have also turned off, being an electric stove. While this is true, she may have been stirring the hot chocolate simply to quell a harrowing and/or awkward moment, instead of just standing there not doing anything. Also, even though the stove is no longer on, there is still residual heat and the hot chocolate may still need to be stirred.
Continuity: When Krug is getting Justin to feel Mari's breast before the rape, he tears Mari's bra away. Later while Krug is raping Mari, her bra is back, and Krug has to tear it away again.
Errors made by characters (possibly deliberate errors by the filmmakers): When John, a doctor, is giving Mari mouth-to-mouth resuscitation, he does not tilt her head back.
Continuity: When the parents try to drown the villain in the sink, he manages to pull the stopper and nearly completely drain the sink, but when they activate the automatic disposal, the sink is once again filled to capacity.
Errors made by characters (possibly deliberate errors by the filmmakers): When Mari's mother gives Francis wine she goes to the fridge and pulls a bottle of red wine out. Red wine should not be stored in the fridge but rather at room temperature.