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 concentrations in the Seine are relatively high. The pH level of the Seine at Pont Neuf has been measured to be 8.46. Despite this, the water quality has improved significantly over what several historians at various times in the past called an "open sewer". In 2009, it was announced that Atlantic salmon had returned to the Seine. The name comes from the Latin , the Gallo-Roman goddess of the river. On 28 or 29 March, 845, an army of Vikings led by a chieftain named Reginherus, which is possibly another name for Ragnar Lothbrok, sailed up the River Seine with