US submarines are designed for speed and stealth. The Navy takes great pains to keep this technology a secret. The most critical part of that secret is the design of the propellers that drive the subs and keep them quiet. Usually, the propellers are shrouded or covered by a large tent. Bird's Eye found this one out in the open.
Note that in most Bird's Eye and Google images, this area is covered by a large tent structure.
Military - Navy and Coast Guard, Sea - Military - Submarines
Links: www.monstermaritime.com
By: jbottero
http://it.slashdot.org/article.pl?sid=07/09/02/1929234
http://cnair.top81.cn/sub/039.jpg