Seafood in DC
I agree with Jason's assessment. Good food; bustling atmosphere; I don't think it takes reservations (at least it didn't used to)--not sure if that's the atmosphere you want.
If you search this page for "Dupont Circle," there's a previous discussion earlier this month on Pesce and other nearby restaurants in Dupont Circle.
Pesce is usually quite good....although it has been cited for inconsistencies over the years. It is quite small and not built for comfort.
For a more romantic dinner with a seafood emphasis, try Sea Catch in Georgetown. For a fabulous meal in comfortable surroundings and the best seafood in DC (in my humble opinion), get reservations at Kinkead's on Pennsylvania Avenue.
You won't regret it.