If one does not use or possess ones own boat, you have to get to Strömstad first and then take a ferryboat "Kosterbåten" to reach Koster.Islands Departure from the north harbor in Strömstad, a pleasant crossing of around 45 minutes.
Welcome aboard the "Kosterbåtarna"
You don’t need your own boat to enjoy a visit to the Koster Islands. Koster Marin operate passenger ferries to the Koster islands all year round.
The passenger ferries depart from the "norra hamnen" in Strömstad at the main square (torget). Street adress Ångbåtskajen, Strömstad. Here you will also find a waiting room with public WC
The ferry stops several places on the islands, both South and North Koster Island. The charming ferry trip takes about 45 minutes, the journey takes about 45 depending on which port you get off at. You can find ferry schedules and other practical information here or or search departures on vasttrafik.se
Tickets can be bought on board (only credit card) or in machines on the quay in Strömstad (credit cards).