Packaged mozzarella wet
There's 2 types of mozzarella, fresh and hard (also called low moisture). Fresh mozzarella is soft and packaged with whey or brine, it tears easily and can be squished between your fingers. It has a relatively short shelf life, usually within a couple of weeks of purchase. If you have this cheese then this sounds normal to me, even a couple of bubbles, if it smells fine and tastes fine I'd think it's safe to eat. 

Hard mozzarella has been allowed to dry partially, and is generally sold in vacuum packaged blocks, with no liquid. It's very firm and shred-able with a grater. If you've bought this and you have liquid and bubbles in the package then I would get rid of it.