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
Blackadder Water and joins with that river at the village of Allanton, where Blackadder House and its estate once stood. The Whiteadder then crosses the English Border below Edrington where it joins the Tweed which empties into the North sea at Berwick-upon-Tweed. Blackadder Water Blackadder Water () is a river in Berwickshire in the Scottish Borders area of Scotland, forming part of the River Tweed system. Rising in the Harecleugh Forest plantation just south of the Twin Law cairns, north of the village of Westruther, the headwaters of the Blackadder join with those of the Wedderlie, Edgar, and Fangrist Burns, before reaching