By: Kevin Trainor/ Managing Editor The marina on Daingerfield Island sits just to the right of the southbound runway of Reagan National Airport. Across from the last airport beacon lies a shallow, weed filled body of water with one clear channel leading from the boat basin of the yachting class to the open waters of the remarkably cleaned up Potomac River. The same river John Smith, and crew, he of Jamestown Settlement fame circa 1609, sailed up. They marveled at the oysters. Oh, the oysters. So visible from the decks through the clear waters then mostly fresh, or salty, depending on the tides. Later, oceangoing cuttys, and other maritime pliers, could still tie up at Georgetown. That harbor locale named for King George II, and not his problematic descendant King George III of the American Revolutionary era. The arrival of civilization redirected the navigable river channel. Later, the most upriver port was Alexandria, just downs...