[Loofa]

Here you go. James Creek Marina‎ , southern tip of downtown DC. Allow you to stay 3 nights in a row, then leave for a night, and come back for 3 nights. Sounds like it's loosely enforced if at all. 8 bucks a foot per month (if you sign for 12 month slip, otherwise 10.25 month to month) Has power, water, and land showers. Lots cheaper than gangplank. Hope this helps,

-Loofa