How can you tell if pływać means to swim or to sail?
Surely, this could equally mean 'I sail every Friday' (if for example you belonged to a sailing club)
Well, the basic meaning is "to swim", but in a proper context it could also mean "I sail".
Yes and no. If it's "Friday", which is only one day, they mean the same thing.
But if you had "w każdym miesiącu", it just means that there is no month when you don't swim. So let's say that you swim three times per week regardless of the month. And "co miesiąc" would mean that you swim on, let's say, 17th October, and then 17th November, 17th December, etc.
Not really English.... You can use "on" in sentences like "I go swimming on Fridays" or "I swim on Fridays", but that weakens the sense of "every" a bit.
"am swimming" is for right now, and "every Friday" is definitely general, habitual, therefore "swim".
Yes, if you're swimming to some specific destination, or at least direction.
But as swimming in the swimming pool, lake etc. is usually multidirectional, just 'swimming around', more often it will be "pływam".
pływać: imperfective, habitual/general, multidirectional
płynąć: imperfective, continuous, unidirectional
Am I right? Also, when I search on Wordreference, I see several variations of both verbs, such as "popływać," "dopływać/dopłnąć." They all describe these verbs as "moving through water" and give no details on their usage. Could you please explain these to me if it's not too much trouble?