One of the main problems with ruggedized (water resistant) phones in general — including Xperia Z line-up, from the very first iteration to the Xperia Z3 — is the fact that the touch screen is almost impossible to use while it is wet. Water droplets totally confuse the device and the wet screen does everything chaotically once the user interacts with the display.
However, with the latest iteration, the Xperia Z3+ (Xperia Z4), Sony seems to have improved the wet screen usability of the phone. Apparently, the smartphone uses a newer touch driver which focuses exactly on this: wet screen usability. We’ll have to properly test it out once we get it in our review labs, but the video embedded below seems to show off the device handling touches pretty well while the screen is being sprayed.