I also saw it when I was a kid and that's why it scared the crap out of me. I was a catholic doing the Sunday school thing, but even at that age I questioned a lot about religion and wasn't totally into it.
I watched it again a few years ago, but I got bored with it because I already knew what was going to happen. I'm one of those who can rarely watch a movie twice without being bored.
Jaws did it for me
and Psycho comes in second for sure and like Phoenix, it's that "it could happen" effect
I use to live in the ocean before that #$%^ing Jaws!!!!
Of course I had to watch all the other Jaws films as well. Might as well since my ocean days past the knees where over anyway