Saimaa marinas and nature harbors list.
From different sources, mostly from "Saimaan Venematkailuopas" and Fonecta map (RIP). And a bit on personal impressions.
Also - my own beautiful views and informative GoodlePhotos.
All of this point are public, as I think.
You may view this files "as is" in any map app, able to obtain POI in csv format. GaladrielMap is a good choice.
Or you may convert it to a preferred format by gpsbabel.
To gpx, for example:
gpsbabel -i unicsv -f StagerSaimaaPhotos.csv -o gpx -F StagerSaimaaPhotos.gpx