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.
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.