what movie is this?

I remember seeing a movie probably 20 years ago now, when I was just a little kid. I don't really remember what it was about, but I remember it had very little dialogue (maybe even just a narrator) and had the same sort of animation style of Bakshi's (I just watched Wizards and it made me think of this movie; I thought for sure Bakshi would have directed it.) It was set against a live action barren rocky landscape on a shore (maybe an island?) and had these two cartoon cavepeople (at least they looked like cave people) trying to fight against these cartoon big blue creatures with spears, and that was essentially the whole movie. I remember the heads of the creatures bearing a strong resemblance to those guys wearing the blue gas masks in Wizards. I remember watching this on tv or on video in probably the late 80's or early 90's, so it was probably an 80's/late 70's movie. I swear I thought the name of the movie was "Id," but I can't find anything on IMDB or Wikipedia or google matching that. If anyone happens to know what I'm talking about, let me know, this may be as obscure as they get.