Corrected entry: When the killer leaves Jen's room (after killing Putman) you hear him slam the door shut. The only door to her room is a patio door, which wouldn't make that slamming noise.
Corrected entry: Near the movie, if you put it in slow motion when the jacuzzi is being attacked for the first time with the axe, you can see the first blow cracking the glass. However, the next time it is hit, a brief shot of the front shows that it is still whole. On the last blow with the axe (keep using slow-mo), no one is inside the pool.
Correction: On closer inspection, you can see that the glass has a small crack in it when he takes his swing. The crack is small so it is a bit harder to see.
Corrected entry: At the end of the film Lars is supposed to be putting the propeller on the boat because it doesn't have one. During this time, he comes out of the water to fight of the killer, and uses the propeller, which falls to the floor. Seconds later, with Lars and the propeller still in the boat, they start up the boat and drive away. But no one ever put the propeller on. There is even a shot underwater of the propeller. A minute after that Lars again uses the same propeller that is supposedly on the boat to fight the killer again.
Correction: Lars has already put the unbroken propeller (recovered from the sunken boat) on before coming out of the water. Frame-by-frame on the DVD shows the propeller Lars uses in the attack to be the old, broken two-bladed one, presumably put back in the boat when the boat was moved from the beach to the floating dock.
Correction: there was a door in the bathroom which would have caused the slammimg noise.