Some years ago, we came across the tri-lingual (Finnish, Swedish, and English) University of Jyväskylä National database of Sports Facilities LIPAS website. It's a bit unwieldy but they make the data available to other users and another site Uimaan.fihas boiled the information down to swimming facilities (indoor pools, outdoor pools, public beaches, and ice swimming venues). It's all in Finnish, but the Chrome and Edge browsers handle the translation fairly well. And it's a commercial site, so you've got the ads to deal with. And, finally, it doesn't directly provide any information about the facility but, rather shows a map and gives a link to its official website. But, if you're in Finland and there's nothing on our site or you're there in summer and you want a seasonal pool, this is probably the best place to look for it.