No he is not. He is merely lucky to have not died yet with all of the wounds he has recieved.
He does die at the end of part 4 when Tommy Jarvis hacks him to pieces with the machete.
He does not appear in part 5 (only in Tommy's dream sequence at the beginning)...........
In part 6 he is ressurected by a lightning bolt..........he is now the walking dead, a zombie.
I was at a huge party a few years back and these kids were messing aroung with a high powered BB gun. They shot a girl right in her eye. The pellet went through her eye bounced around in her brain and stopped!!! she collapsed and we rushed her to the hospital. she is fine now, so you can take major brain trauma and live, however it was pretty gross to see blood gushing from her eyeball!!!
GRRRRRR..................some people did not pay attention to the movies!!!
The mythology changed at the end of part 8.
Jason did not originally drown in the lake!!!! Watch the beginning of part 2 again. Pamela Voorhies THOUGHT he had drown........and sought revenge on camp councilors, because she blamed the councilors for his death. Jason did not drown. He found an empty cabin in the woods and grew up there......that is why he is an adult now. It even shows his cabin/shack in part 2. He was ashamed of his appearance so he never ventured out of the woods. He was in the woods watching when his mother was killed. He then sought revenge for her death. Still ashamed of his looks, he wore a burlap sack over his head when venturing out .....even to kill people.
In part 4 Jason if finally killed......only to be ressurected in part 6 (he doesn't appear in part 5). His body is struck by lightning bringing him back to life. He is now a zombie....the walking dead.
This story continues all the way up untill part 8, then they change the story. At the end of part 8 Jason reverts back to a little child at the age he would have been when he was thought to have drowned. They changed the story to say that he HAD drowned as a child. This story continues through part 9 and Freddy v/s Jason (don't really mention it in Jason X).