One of the main selling points of Sony’s line of Xperia smartphones is the IP68 water and dust resistance. Which would be a great selling point if not for the fact that people have been trying to use the devices underwater; damaging the device in the process. It turns out that IP68 rating only applies in some very specific circumstances.
Sony Mobile has a page explaining what exactly IP68 means; and how it is tested. It turns out that Sony only had to ensure that the phone is able to function after being submerged under 1.5m of water; and not while it is underwater. In Sony’s own words “after 30 minutes in the container, the device is gently taken out and its functions and features are tested”.
Despite the misleading marketing message, it appears that Sony’s Xperia phone were never meant to operate underwater. Sony has been using promotional pictures of the Xperia smartphones being use to take pictures underwater, which has had the effect of getting consumers to try it for themselves. This writer has had at least one friend who discovered the lack of aquatic functions on the Xperia line.
There are other instructions for maintaining the IP68 water resistance rating, which includes allowing the device to dry properly and rinsing it down if it comes into contact with chlorinated water or seawater. It should be noted that the updated warning was originally posted for the Xperia Z4/Z3+, but appears to now cover the newly announced Sony Xperia Z5.
Basically, do not trust the advertisements when drawing conclusions about the water resistant capabilities of any device. Although Sony could have tried to make this more clear before people actually went out to try taking underwater pictures.