Once a year in July there is an event close to our home with old time 'post boats', that a team (5-6 p) rows between Finland and Sweden, where the distance is shortest namely between Holmön (close to Umeå, Swe), and Björkö (close to Vasa, Fin). The distance is around 60 kilometers, and it takes from 6 hours to a day. In the old days mail were delivered by boats between Fin and Swe, as Finland was part of Sweden. You can watch this short clip, even if it's in Swedish.
https://youtu.be/59gZPb5uuRM