Dancers on the edge of reality

I've been re-editing some of my old gifs, and since there are several thousand of them - yes, that's right - this could  take quite a long time. I edited four gifs together in this one, and I have no idea what the source material is or where I got it. It looks like a negative of a black-and-white film, and I don't think I created that effect myself. If I did, I don't remember how I did it.

This was a very small gif originally, and making it any bigger affects resolution. So I left it this size. Who ARE these people, I wonder - when did they perform this? On early TV, as I suspect? How did they achieve these camera effects? They almost seem to be dancing underwater.