National Harbor, the mile-and-a-quarter-long waterfront development under construction just south of the Wilson Bridge in Prince George's County. Riverboat Company and Milt Peterson, founder and chairman of Washington, D.C.-area developer, The Peterson Companies, which is developing the mixed-use project, announced today that the Potomac Riverboat Company will begin seven-day-a-week water taxi service between the two riverside destinations in April 2008. Two newly-commissioned 99-passenger boats, which are yet-to-be named, will run initially on the half-hour between 10 A.M. and 10 P.M., providing 50 one- way trips daily between the Alexandria City Marina and the Commercial North Pier at National Harbor. The crossing is expected to take 20 minutes.