I brewed this beer on Tuesday, and I am fermenting it in an open bucket type fermenter with a (clean) towel draped overtop. I drew a sample today to taste and take a SG reading. After I did the reading, I tasted a few mouthfuls; and it was definitely fizzy. Not really fizzy like soda, more like carbonated water fizzy (like the kind often served in Italy). I've never encountered anything like this before.