Aker brygge, Lindøya, Hovedøya, Langøyene, Nakholmen, Bleikøya, and Gressholmen. These are the names of the islands in the inner Oslo Fjord, connected by ferries.
There are four different ferry lines with individual marchroutes which tourists can use to hop on and hop off between islands.
Island hopping doesn't even need to be a guided tour experience. We advise you to take all the time you need and enjoy what's most enjoyable for you. The regular public transportation ticket, as well as the exclusive Oslo Pass for tourists, are all you need to use the ferries. The rest is up to you.