DC isn't a port city. If he wants a port city, he should go on back down to Hampton Roads. Besides that, most of the attacks have been outside of DC. One shooting in DC, the rest in Maryland or Virginia. And Bull Run, the closest body of water to Manassas, isn't exactly a big highway of water commerce these days. Fredericksburg isn't anywhere close to a port, either. Can't speak to the water near the MD shootings, but none of these killings has taken place in the bosom of a port city, not even the DC shooting.
The one shooting in D.C. was just barely inside D.C., just south of the boundary with Montgomery County, MD. In fact, as I determined from personal observation on Saturday, the sniper may have shot from inside MD: from the roof and upper stories of the Ramada Inn three or four blocks of the place where the victim was hit, you would have had a clear line of sight to the victim -- and the Ramada Inn is in Montgomery County, MD.