This picture was taken when my friend took me to have a photo tour along the coast of Marine County north of San Francisco. I was at the time on my "Long Way Back Home" from Cape Cod to Taipei. When we look out to the Pacific Ocean toward the west, we saw this black spot over the horizon. It look like that it was in the sky/cloud. When we look through the telephoto lens, it was a tanker with a tugboat on the side.