Jason was always a "Zombie" *spoilers*
I've read in numerous places and seen other people talk about this and I wanted to put this out there because it annoys me. Whether you want to use the term Zombie or whatever, the movie makes it pretty clear that Jason was always dead. He died when he drowned in the lake, and I'll use NUMEROUS examples from the first four films to illustrate my point. Obviously NUMEROUS spoilers ahead for the first 4 movies.
Number 1) The mother went completely BAT *beep* crazy because her son died. The whole "chi chi chi ka ka ka" thing is ACTUALLY "ki ki ki ma ma ma" and represents Jason telling her to kill people in her mind. She also a few times speaks as if he were inside of her telling her to kill the counselors. I'm not suggesting there is anything supernatural about this (though who knows, maybe there is), she's just completely crazy. People DO tend to go crazy when their kid dies, ESPECIALLY if they believe that death was due to negligence, this is normal I think (though the killing probably isn't normal, but not outside the realm of belief either). Wouldn't make any sense at all for her to go THAT crazy if her kid didn't actually die.
Number 2) Jason comes plying out of the water at the end of number 1, and he's severely decomposed. People like to make the argument that this was all a dream which is completely absurd. They showed the ripples in the water at the very end of the SUGGESTING that Jason was still there AND we had 11 movies after this one showing he's still around. The SIMPLE answer is he came out of the water after her because he saw her kill his mother. Otherwise what we are talking about is one hell of a monumental coincidence that she just HAPPENED to imagine Jason coming out of the water 2 years (I think) before he would later appear and start killing people.
Number 3) People don't catch a machete to the clavicle and then get up and start running around and killing people again. You know who does that? The undead.
Number 4) People don't get hung, hang there for a minute (and probably snapped their neck on the way down) and then all of a sudden wake up and pull themselves off the rope. You know who does that? The undead.
Number 5). People don't catch an ax to the forehead and take a nap for a few hours, only to wake up later and start walking around like nothing happened. You know who does that? The undead.
Number 6). People don't catch a machete clear through their head and are still alive on there way down to the ground like he did at the end of 4, and they certainly don't continue moving around afterwards like their thinking about getting back up. You know who does that? The...hell the undead don't even do that, that's all Jason.
I also want to point out the absurdity of believing he didn't drown. I can't think of a plausible scenario where a mentally retarded child goes under the water and nobody ever sees him come back up and he doesn't drown. You what, want us to believe that this mentally retarded child who couldn't swim "very well" (according to his mother) some how managed to get out of the water without anyone's knowledge and then go on to survive in the woods all alone with out anyone's help? I mean we're talking about a mentally retarded little boy hunting, fishing, foraging for food that isn't poisonous. Doesn't make any sense at all. It's actually more believable that he died and came back from the dead, I would probably believe that in real life before I would believe that he managed to survive on his own in the wilderness.
I know there are probably NUMEROUS other examples in the first 4 films but I think I've made my point. The guy was always dead, he died in the lake and then came back. I'm assuming after his mother died but who knows maybe not, maybe before.
By the way, I am right behind you.