Basically, when it comes to IPX/X certificates, it can be pretty easy to break down the figures. The first digit is always an indicator of the level of protection from dust ingress, while other digit shows off the level of protection from water. Most of the protected devices on the market today happen to be resistant to either dust or water, and are not foolproof, although the Sony Xperia M2 Aqua seems to defy all odds.
The IP6X certification points to it being wholly dust tight, while the IPX5/X8 segment means it can hang around underwater for more than half an hour – as long as it is no deeper than one meter of water. I am quite sure that the Xperia M2 Aqua will be able to hold its own as well if it were to be subjected to similar conditions in the Samsung Galaxy S5 torture test. All in all, this looks like a decent waterproof smartphone if you are on a tight budget.