So "pływać" can be "to swim" or "to sail," but "pływanie" can only be "swimming"?
Generally, "to sail" is "żeglować" (but rather provided that you really, literally have this sail - I think it's not necessary in English?) - but 'pływać' can work as well.
And as "sailing" is concerned... well, without any context, I don't think I would think of 'sailing' when hearing "pływanie".
Thank you! So, if we were having a conversation about sailing, I might be able to say "Pływanie to ciekawe hobby," since there would be context, but it wouldn't be the best way to say it?
Well... I guess I would specify the... type of boat on which I usually sail. Unless it's literally a sailboat, so then I'd say "żeglowanie" or more probably "żeglarstwo".
Also, I have no real knowledge on that topic, so there's a possibility that someone who does can disagree.
I thought the word 'ciekawe' gave context as swimming is a purely physical activity and 'interesting' implies something a bit more cerebral, such as choosing a course to suit the conditions when sailing. Probably overthinking as usual :)