I haven't held a g3 yet but its build looks a lot like the galaxy line of phones and the only things they added to the s5 to make it water resistant is a small bead of something on the lid that acts like weather stripping and a water tight lid for the usb 3 slot. Just add a bead of caulking to the g3 lid and buy a case with a usb cover. I bet you would be just as water resistant as any phone that is right out of box.
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