As a beltway guy myself, I had to hop in. (btw, Keepusfree, I hope you took my comments with the needling spirit they were meant in, rather than personally)
The DC area is home to one of the classic kayaking locales of the entire Eastern U.S.: the Potomac River Gorge (including Mathers' Gorge), which extends from Great Falls, MD-VA to Georgetown, DC. It claims to be home of the most globally rare habitats of any place in the entire U.S. I used to have to cross Chain Bridge over the gorge every morning. Because it's a bridge completely incapable of dealing with its traffic levels (3 lanes total for both directions), it's always jammed. But I learned to relax, enjoy the midmorning break, and watch for the bald eagles, which for a little while became a daily sighting for me!
I was just kayaking at Angler's Inn last Tuesday...in fact I got interviewed by TV crews and Newspapers (about 6-7 of them!) as we were putting on. I was probably on some news show in DC somewhere (I'm not from DC....so I never checked any TV or Papers)