Reboot iphone

Liquid damage could have reached internal components, corroding them. But we can't diagnose your issue remotely, sorry.

Have your device inspected at an Apple Store or Authorized Service Provider. After checking it out, they'll give you all the available options:--> Apple – Location Selector

Regards

Giulio

You device has been destroyed by the water and can't be repaired.

Water damage is not covered by the standard warranty and the device must be replaced.

Take it to a recycle center.