The Blavet river flows from central Brittany and enters the Atlantic Ocean on the south coast near Lorient. It is 148.9 km (92.5 mi) long. The river is canalised for most of its length, forming one of the links in the Brittany canal system. It connects with the Canal de Nantes à Brest at Pontivy and runs to Hennebont, a distance of 60 km. From the last lock at Polvern, the river is tidal and considered as a maritime waterway, giving access to the seaport of Lorient and the Atlantic Ocean. It became more important when the western half of that system was cut off by the construction of the Guerlédan dam and hydropower plant. Today, boats coming from Nantes via Redon have to take the Canal du Blavet in order to reach the ocean near Lorient.