The easiest way of getting to Kökar is either using the southern line of the ferries, or by your own boat. The ferries of the southern line depart from Galtby in Korpo, Finnish mainland, once or twice daily, and from Långnäs in Lumparland, Åland mainland, 3-6 times a day.
The southern line, touching at the harbours of Långnäs, Överö, Sottunga, Husö, Kyrkogårdsö, Kökar and Galtby, carried almost 100.000 passengers and 35.000 vehicles in 2015.
At Havsgården (site in swedish and finnish) on the island of Kyrkogårdsö, you'll find charterboats.
On Kumlinge you'll find the company Ålands Båtar, providing boat taxi services in the archipelagos of Åland and Åboland.
You may order the boat taxi at phone +358 40 506 1299.