Some years ago, I was a "guest crew" on the tall ship "Pride of Baltimore," and sailed from Annapolis to Alexandria and passing National Harbor on the way. Nice trip but we motored most of the way up the Potomac. I was at the helm when we passed through the area that Bill Roosa describes quite accurately just north of the Rte 301 bridge. Keep a close eye on your depth sounder and an eye on the chart as there are many charted and some uncharted shoals there. National Harbor is a nice place to visit with lots of good, albeit expensive, restaurants.