Youtube user Streetcap1 found an anomaly in a NASA photograph that appears to be a five-mile-wide black disc floating above the ocean. The disc can be seen on a picture that was taken in November 2013. The picture in question is still available in the website of NASA.
According to the one UFO website, the suspected space aircraft is actually hiding underneath the ocean, though it appears to be over it. This website says that the dimensions of a large object are nearly perfect and could be over 5-7 miles across.