I was a movie projectionist in the '80s and I showed Jaws 3D. The film was on standard 35mm stock, but each frame was divided horizontally, with the image intended for the left eye on the top and the right-eye view on the bottom. The print came with a bulky, black metal box which fit onto the lens of the projector. This box had mirrors inside which split the picture and superimposed the left and right images and passed each through a piece of polarized glass. The audience would then, of course, wear glasses with similarly polarized lenses, isolating each image to one eye and creating the 3D effect.
Here's the problem: the lenses on those old, cardboard 3D glasses were REALLY dark. The polarized glass on the 3D projector gimmick was really dark. It was basically like watching a movie through two pairs of sunglasses. Add that to the reduction in resolution from blowing half a film frame up to full-screen along with the darkness of the underwater scenes and it made for a very murky experience. Universal actually paid to replace the standard white screen in the theater with a silver one to increase the amount of reflected light reaching the audiences' eyes. It didn't help much.
It was interesting watching Jaws 3 in 2D and in full brightness. I think maybe the dimness of the theatrical release may have worked in the movie's favor.