Water under phone screen: showing vertical white lines

hi,

It all depends on where the water went to after it got into your phone. Best bet is to open your phone (check out repair guides on here if unsure) and have a look at any water damage indication. The top right of the phone is where you have the flex cables, so water could've got onto there and short-circuited the cables. You will need to take the screen off, check for water damage and clean all the connections for the flex cables. Let it dry out before reconnecting. I always find a 'power cycle' of the battery helps. (disconnecting battery from its connector, waiting 30 seconds and plugging back in again)