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".
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.