@Emanuele85
I'm sorry to say this but the phone its water resistant not waterproof
*** Xperia X Performance is water resistant and protected against dust, so don’t worry if you get caught in the rain or want to wash off dirt under a tap water, but remember all ports and attached covers should be firmly closed. You should not put the device completely underwater; or expose it to seawater, salt water, chlorinated water or liquids such as drinks. Abuse and improper use of device will invalidate warranty. The device has been tested under Ingress Protection rating IP65/68. For more info, see www.sonymobile.com/waterresistant . Note the Xperia™ X Performance has a capless USB port to connect and charge. The USB port needs to be completely dry before charging.
I don't think the warranty will cover this but since this is a global user based forum, you might want to contact your Local support to get it inspected, perhaps omit the part of submerging the phone in the pool.
