If you want a boat trip on the fjord, there are several options in Porsgrunn municipality. The boats from Brevik runs regular routes to the archipelago outside Brevik all year round.
MS Dikkon runs regular sightseeing tours to the archipelago outside Brevik on Wednesdays and Saturdays in July.The boats from Canal Boats Telemark are 100% electric and you can rent them on a weekly basis or for shorter periods of time. You can take the trip up the Telemark Canal or a trip along the fantastic Telemark coast.