Other mistake: There is a lot of bad continuity over how many vehicles there are. First there is Jeff's truck then Ginny shows up in her car. Later Paul says they only have two vehicles when they decide who is going to the bar. Later we see Vickie go to her own car when she's looking for her hair brush, so that's actually three vehicles. But there are at least 15 people at this camp. There would have to be more vehicles somewhere.
Other mistake: When Jenny is hiding in front of the yellow car you can see the top of her head yet Jason doesn't see it.
Other mistake: When Jason sneaks up behind the cop and raises the hammer to whack him, the angle shows it aiming for the cop's neck, but in the continuing shot, he strikes the back of the cop's head. (00:45:35)
Continuity mistake: When Jason comes smashing through the window at the end, to attack Ginny who is getting up from the cot, the camera angles are inconsistent with the attack. First he is lounging at her from behind, to grab her. Then his distorted face is suddenly at her left shoulder before he's even touched her Then she's looking back at him and screaming before his hands even touch her and pull her out of the window. (01:24:20)
Revealing mistake: When Jeff and Sandra are in the woods, they bend down to examine a mangled animal. You can see that the animal has human teeth, not animal teeth.
Other mistake: Vicki enters the darkened cabin and flips a switch on a nearby lamp, to discover the power is out. But as she grumbles and crosses to another table lamp that is unplugged, she plugs it in, and suddenly the whole cabin lights up.
Plot hole: While underwater all of those years, Jason didn't seem to age. He seemed to be a child when he grabbed Alice at the end of the first film. How could he grow up to be an adult after only five years, as Paul stated during the campfire story?
Suggested correction: Dialogue in the film hints at what actually happened, which is that the end of the first movie was some sort-of panicked dream/delusion Alice had, while the real Jason has been living out in the woods ever since he "drowned," and thus aged into an adult. (Whether he actually did drown and came back to life, or escaped and fled out into the woods because he was mentally challenged is up for debate.) It's admittedly shaky, but the movie does hint at an explanation, so I don't think this really counts as a mistake.
