Still, i think i gonna go through with it, to see how it goes. Don't worry, swimming is very slow, therefore you can't swim a long distance without starting to loose health : in the end it's not that great an advandtage. Plus i realized while playing that there were some chokepoints which you cannot go through without being seen, making sneaky tactics and capturing very hard. And about the realism of non-transparent water, i'm not sure about that, because it really depends on the geographic region : in some places you can't see past 30 cm of water when the sun is low.
Anyway, don't worry it's still a beta, it very much may change.