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
6th Airborne Division advance to the River Seine by German armour and infantry, the division's position was secure by the end of the Battle of Breville on 12 June. Thereafter, they suffered only artillery bombardments. Almost two months later on 7 August, the division was warned to prepare to advance. Their objective would be the mouth of the River Seine. To reinforce the lightly armed and equipped airborne division, the British 1st and 4th Special Service Brigades, together with the 1st Belgian and the Netherlands Infantry Brigades were placed under their command. Additional artillery support was provided by two field artillery regiments, a medium artillery battery, and a