You've gotta be savvy about the waterproofness. Yes it's watertight brand new but overtime those silicone seal flips gather dirt the more theyre opened. If there's dirt on them it won't be watertight (we're talking really small dirt particles).
This won't be an issue in rain or the odd splash but submerging the phone is a different matter. The key is to clean the seals, if you don't you could well find droplets appearing on the camera lenses or worse still you can fry the mainboard.
Its pretty easy to clean them with cotton pads or similar, I do it one every 2 months on my Z, Z1 and now my Z2. They never opened by themselves like others do. Takes about 2 minutes to clean the inner edges of the port and then you're good to go.
Z3 owner here, love the device. It really is a beautiful piece of kit (white). Android I can't say I love, but the app situation is so much better than with Windows Phone it totally outweighs the minuses.
Not had the chance to test out the water proof features, but considering I bought the device handset only I will be wanting insurance first!
If you want to check out if your phone is waterproof then close your lids and open your dialer and tyoe in this:
1. dial *#*#7378423#*#*
2. go to "Service Tests"
3. go to "pressure sensor"
Or download any barometer app from the store.
Now open the app or pressure sensor and start squeezing the front and the back and check the pressure to see if it is moving. If its moving up and then slowly down you're good to go. But if absolutely nothing is happening then you might hold yourself off from watertesting it