Scariest Movie

I believe that this is the first time I've actually followed one of the prompts.  Normally, I don't feel like I could write very much with any of them, but this might be somewhat different.  The last movie I saw that scared me was a movie I watched when I was three, and that's the truth.  For some reason, they all seem to be just movies.  The reason the one I watched when I was three scared me was because, well, I was three.  The part that I remember was people being on a submarine for some reason, I know they were not military.  Suddenly, robots appear and take over the submarine, killing everyone.  However, it's not enough to just kill them, but they dissect their bodies afterwards.  The movie showed fairly realistic brains for the time, and most of the lights were off when people were killed.  These two were terrifying because I was a little squeamish from blood and still a little scared of the dark.  That movie still seems scary to this day, although it probably would not be if I watched it again.  It's too bad that I don't have any idea what the name of the movie was.  My sister had rented it for Halloween.