The Oslofjord (Norwegian: Oslofjorden, Urban East Norwegian: [ˈʊ̂ʂlʊˌfjuːɳ]; English: Oslo Fjord) is an inlet in southeastern Norway. The 120-kilometre (75 mi) fjord begins at the small village of Bonn in Frogn Municipality and stretching northwards to the city of Oslo, and then curving to the east and then south again. It then flows south to an imaginary line running between the Torbjørnskjær Lighthouse and Færder Lighthouse where it becomes part of the Skagerrak strait. The Skagerrak connects the North Sea and the Kattegat sea area, which leads to the Baltic Sea.
https://en.wikipedia.org/wiki/Oslofjord