This awesome photo is of a US Navy Blue Angels jet flying low on the water of San Francisco Bay - check out the sonic boom (?) as the jet flies amidst sail boats.
Link - via Cellar Image of the Day (great discussion, including the invariable inevitable "photoshop!" allegation and more pics there)
http://en.wikipedia.org/wiki/Prandtl–Glauert_singularity
For video of this phenomenon (which looks a lot like the same fly-by that produced this photo), check out this link. It's ranked the #1 low fly-by, so you have to watch to the end:
http://biertijd.com/mediaplayer/?itemid=19448*
http://home.comcast.net/~bzee1a/FleetWk07.html
http://www.navy.mil/view_single.asp?id=34239
051009-N-7559C-001 San Francisco, Calif. (Oct. 9, 2005) - The Navy's Flight Demonstration team, the Blue Angels lead solo, performs the sneak pass, a maneuver that demonstrates the F/A-18 Hornet's ability to sneak into a target area undetected at speeds approaching 700 mph. The Blue Angels perform more than 70 shows at 34 different locations throughout the country each year. U.S. Navy photo by PhotographerUs Mate 2nd Class Ryan Courtade (RELEASED)