Does it float?
Yes, it floats, as long as there air in it and the item in it does'nt weigh a ton.
There is a little bit of padding in the back of it that makes it float when nothing is in it. Most smartphones have a density that is greater than seawater, so make sure you leave enough air in it to prevent it from sinking. As the previous reply said, just apply Archimedes' principle and make sure there's more volume (in fl oz or ml) than there is weight (in oz or grams).
yes floats, I love the thing, bought 4 of them, can take and use the cell phone on the Seadoos. the blue back is 2 ply and has a thin pocket of air in it so naturally buoyant. I've tested it, thrown my phone in the water in it, it floats and stays nice and dry
Yes, as long as what you put in it does not weigh more than an equal volume of water. For most cell phones, handheld GPS, etc. that would mean it should float.