It happens now and then here, its not the first time its been documented either. Here is another story where a family witnessed a floating cow and ufo:



In english what they are saying:

We went to have some mate with the kids, we were looking at the island and we were surprised to see some strange white thing flying. It was large. We made a close up with the camera and it was a cow flying, and above it, there was something like a flying saucer suspended in the air. It wasn't a helicopter or an airplane. It seemed as if the cow was being sucked up by the flying saucer. Then they both vanished. I want to believe that's what it was. To me, it was a UFO.