I think if you add in 'sempre' to the sentence- La mosca beve l'acqua sempre (although I'm not sure if sempre would go at the end of the sentence or not..) And, as for drinking the water now, aside from using the present tense 'beve', you could also say "La mosca sta bevendo" which combines 'stare' and the gerund, which is the 'ing' in words, it would be translated as "the fly is drinking water" and it is implied that the action is happening now. I hope that makes sense and helps :)
I just heard that Italian is one of the easiest languages to learn in about 600 hours(25 days). I've been using Duolingo for a while now, and I still haven't started learning how to properly use sentences like how to order something, or how to ask a question, even though I set my goal to learn languages for travelling...can someone please tell me, how is a sentence "The fly drinks water" (or similar sentences) going to help me with travelling?!