UFO Sighting in Buleleng, Bali on August 1st 2015 – UFO appearing on a classical sunset photo few days after being done

I took this picture at Lovina Beach (North Bali). I was taking many pictures of a beautiful Sunset (many other people do the same here, the spot is reknown for that). Few days after I saw an object on the picture and it is a UFO. When I took the picture, I saw nothing, neither the people around. I took another picture on the same minute just before and nothings appears, and the next one 2 minutes after and nothing appears either. So it might have moved very fast. The form of it is very precise as a "half a sphere".