It is not meant to be used under water. But it IS water proof.
Now may I show you the following chart:
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"Watches are often classified by watch manufacturers by their degree of water resistance which, due to the absence of official classification standards, roughly translates to the following (1 metre ≈ 3.29 feet):[5]
Water resistance rating Suitability Remarks
Water Resistant 3 ATM or 30 m Suitable for everyday use. Splash/rain resistant. NOT suitable for showering, bathing, swimming, snorkelling, water related work and fishing. NOT suitable for diving.
Water Resistant 5 ATM or 50 m Suitable for swimming, white water rafting, non-snorkelling water related work, and fishing. NOT suitable for diving.
Water Resistant 10 ATM or 100 m Suitable for recreational surfing, swimming, snorkelling, sailing and water sports. NOT suitable for diving.
Water Resistant 20 ATM or 200 m Suitable for professional marine activity, serious surface water sports and skin diving. Suitable for skin diving.
Diver's 100 m Minimum ISO standard (ISO 6425) for scuba diving at depths NOT suitable for saturation diving. Diver's 100 m and 150 m watches are generally old(er) watches.
Diver's 200 m or 300 m Suitable for scuba diving at depths NOT suitable for saturation diving. Typical ratings for contemporary diver's watches.
Diver's 300+ m for mixed-gas diving Suitable for saturation diving (helium enriched environment). Watches designed for mixed-gas diving will have the DIVER’S WATCH L M FOR MIXED-GAS DIVING additional marking to point this out.
Manufacturers water resistance classifications are interpretations and are not part of any ISO standard definition."
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Now, as you can see the very watch you wear on your wrist is not what you thought it was in terms of being water proof...
I can assure you nothing man made that I know of at present is water proof. I have written this in at least a dozen threads on this forum and still posters fail to understand the difference. Not even a submarine is water proof as one member commented. Take a sub past its operating depth and you know what will happen to it...implodes like an egg shell.
There is an awful lot more to this water resistance too. When Sony show an XZ in water that water is still, this is highly significant as passing water over the face of the phone will further reduce its water resistance. That is why a watch rated as water resistant at 30M is STILL not suitable to take even into a shower.
Sony have been rather unwise to show some ads with the phone sitting in a small bowl of water. This will make customers think the phone is water proof. Though Sony CLEARLY state in the instructions the mobile is only safe to a given standard there are already people using them in the shower, bath and even sauna. Now add to this already difficult scenario and add temperature to the equation and we have a phone that is in truth accidental water contact resistant to a very specific degree and nothing more. Sony merely wanted to show the phone could take some contact with water like wet hands, use in the rain etc.
The XZ is a domestic phone, if we want a more robust mobile look at the new CAT mobile now that is built like a brick and is an entirely different animal to our slim and elegant XZ
I strongly respectfully suggest one keeps the XZ away from deliberate water contact. It is not an industrial phone.