First, you're going to have to define what the acceptable commuting distance and time is for you? How far you willing to commute? How much time are you willing to spend in the car? Also, where in DC are you going to be working? Downtown, NW, SW, SE? Virginia or Maryland perhaps?
Marinas around the Magothy and Patapsco are only about 45-60 minutes from areas such as Bethesda, Chevy Chase, and Rockville. With the new ICC (MD Rt 200, toll road) maybe even less (the ICC cuts 20 minutes off my commute to Glen Burnie from Rockville, otherwise its about 60 minutes)
If you're working in downtown DC you could look at Annapolis/Severn and the South, West, and/or the Rhode Rivers.
Herrington Harbor area is also a popular choice with lots of marinas, Herrington Harbors Marinas are two of the best of the bay.
Solomons is also worth a look, but may be a bit far to commute?
You may already know this, but the traffic in and around DC, especially during rush hours (think 6:00 AM to 10:00 AM and 3:00 PM to 7:00 PM) sucks! The only road that is not jammed is the new ICC = $$$$$ to drive it.
You will probably have better luck finding live aboard marinas around Annapolis? Not certain though.
If I were moving to the general area and wanted to live on a boat and work nearby, I would really consider Baltimore, DC is not much of a sailing/boating town IMO.
Just a couple of thoughts FWIW