NOT waterproof, from the Apple site, hidden down the bottom
"*Apple Watch is splash and water resistant but not waterproof. You can, for example, wear and use Apple Watch during exercise, in the rain and while washing your hands, but submerging Apple Watch is not recommended. Apple Watch has a water-resistance rating of IPX7 under IEC standard 60529. The leather straps are not water resistant."
Maybe waterproofing will come out in an OS update? They added that to the iPhone didn't they?