To show off the waterproof features of the Sony Xperia Z1S, Sony developed a series of three Underwater Apps that are designed to be used underwater. The Sony apps like Plantimal, Rainy-oke and Goldie make use of ultrasound technology to detect when a phone becomes submerged in water. When this happens, the apps come to life, and Sony humorously notes that the "apps gives you things to do with a waterproof phone—other than drop it in the toilet."
This 30-second ad for the Plantimal app shows the game off as like a cross between something like a Tamagotchi and Sea Monkeys, where you're required to water your sea plant to make it grow over time. The apps are available to download from the Google Play store, and they're definitely worth trying out, especially since not a lot of other phone companies encourage you to dunk your smartphone in water.