Seine Commercial craft (barges and push-tows) can use the river from Marcilly-sur-Seine, to its mouth. At Paris, there are 37 bridges. The river is only above sea level from its mouth, making it slow flowing and thus easily navigable. The Seine Maritime, from the English Channel at Le Havre to Rouen, is the only portion of the Seine used by ocean-going craft. The tidal section of the Seine Maritime is followed by a canalized section ("Basse Seine") with four large multiple locks until the mouth of the Oise at Conflans-Sainte-Honorine (170 km). Smaller locks at Bougival and at Suresnes lift the
Seine River Crossing at Mantes-Gassicourt August. Seine River Crossing at Mantes-Gassicourt General George Patton's Third Army's Seine River Crossing at Mantes-Gassicourt was the first allied bridgehead across the Seine River in the aftermath of Operation Overlord, which allowed the Allies to engage in the Liberation of Paris. During the two days of the bridge crossing, American anti-aircraft artillery shot down almost fifty German planes. After the successful allied invasion of Normandy in June 1944, The United States Third Army was formed in France to assist in the breakout from Normandy, code named Operation Cobra. The drive to the Seine began on 3 August, when General