In Oslo you have a number of places to choose between for swimming in the outdoors. You can swim both in the fjord and in the lakes in the woods.

Akerselva (Frysja, Brekkedammen, Stilla): Recreation and swimming area along the river between Maridalsvannet and the city centre.

Bygdøy (Bus 30):
Huk: Oslo's most popular beach for young people.
Paradisbukta: Popular and sandy beach for children.
The Islands (Ferries from Vippetangen): Hovedøya, Langøyene, Gressholmen (Heggholmen and Rambergøya).

Oslo South ("beach bus" no. 87):
Solvikbukta, Malmøya
Fiskvollbukta
Nordstrand bad
Katten
Hvervenbukta
Bestemorsstranda
Ingierstrand bad

Oslo forest area:
Sognsvann: Subway 3.
Bogstadvannet: Bus 41.
Badedammen Grorud, Lillomarka: Subway 5 to Vestli, bus 32, 62, 68, 79, 362 to Grorud.
Trollvann, Lillomarka: Bus 56 (from Torshov) to Trollveiskrysset.
Vesletjern, Lillomarka: Subway 5 to Kalbakken st.
Steinbruvann, Lillomarka: Subway 5 to Vestli, bus 32, 62, 68, 79, 362 to Grorud.
Ulsrudvann, Østmarka: Subway to Ulsrud st.
Nøklevann, Bråten badeplass, Østmarka: Subway to Bogerud st.
Lutvann, Østmarka: Subway 2 to Haugerud.