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–Nord Europe Canal Lys/Leie in Flanders and on the waterways in Wallonia. It will run 107 km from just north of Compiègne, to the Canal Dunkerque-Escaut, crossing the regions of Picardy and Nord-Pas-de-Calais. The 107-kilometre-long canal will connect the Seine and Scheldt rivers and facilitate inland water transport. When the new Seine-Nord connection is ready, it will allow large vessels to transport goods between the Seine river (and the Paris area) and the ports of Dunkerque, Antwerp, and Rotterdam, or further into Europe. The canal will replace the Canal de Saint-Quentin and the current Canal du Nord, increasing maximum barge capacity from 650