Screen freaking out - appears similar to a dead PC GPU

Not sure what happened but my Galaxy S5 screen has been freaking out. When I turn the phone on the start up screen scrolls upwards at varying speeds. Once the phone is turned on the display switches between being offset from the screen, and throwing a horizontal colored mess.

It looks very much like when a PC GPU is going out. IE: https://i.stack.imgur.com/K5kVc.png

The phone had water ingress several months ago but has been working fine since then (did the rice thing). This really did come out of nowhere one day.

So, what do yall think, is it the motherboard or the LCD? And if it is the motherboard, is the storage built onto the board?(I have some things I haven't backed up)

Thanks!