Light-distortion moved methodically across San Francisco Bay to above Treasure Island, dropped, returned along same path.3 of us were sitting on a rock outcropping with a good view of San Francisco after dinner. Persons 2 and 3 were busy discussing classes. Person 1 noticed a strange shimmering that seemed to appear in front of the Golden Gate Bridge, after which it began to move south. As it passed in front of the city lights, the lights in a small spherical area would become distorted (brighter and wavering), and return to normal as the object moved farther left in the field of view. Person 1 pointed the object out to Persons 2 and 3, neither of whom could pick out the object until Person 1 told them to look at the TransAmerica Tower and told them exactly as the object passed in front. They then all followed the object with their eyes as it continued to move slowly southward over the Bay. The object stopped directly above the island that cuts the Bay Bridge in half (Treasure Island I think it's called?), and we lost sight of it as it dropped directly down and out of our line of sight to the buildings (again slowly). We started talking excitedly about what we had seen before Person 1 again noticed the object; it had risen back up to roughly the point from which it started its descent. The object then returned along the same path it originally took. As it came in front of the Golden Gate Bridge again, it began to shrink rapidly and move slowly upwards in our field of vision until it no longer distorted the Golden Gate Bridge lights. It seemed to be moving away from us at this point, but we could be wrong as well; we could not, after all, see the object, but only the circular pattern of distorted light. I am "Person 3."