It's waterproof in the sense that it isn't damaged by water. If you unclip and see the contacts are wet, then they simply need to be dried off. I never had any waterproof issues with 7 or G4. Sometimes I've layered tape over the top side of sensor while showering, but this is mostly to prevent water from getting near the adhesive, so it could stay stuck a little longer. I use my Dexcom while exercising all the time, and while the "???" does happen occasionally, it hasn't been a major issue for me.
