Yes. There are several areas for water front properties in Prince William in the $400K price range. Lake Jackson in Manassas, the Occoquan River, the Occoquan Reservoir all have very nice homes on water front lots in the price range.
There is a really nice waterfront home on a small lake in the Gainesville area just west of Manassas with lots of frontage on the lake. Electric motors only. Peaceful setting but close to commuter routes and major shopping. The home is appraised over $500,000 but is just listed at 499,900, with fleibility. See PW6188598 at http://www.mjdimino.com