system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how exactly does water ruin electronics, assuming that they are turned off after and dried throughly, what damage to hardware is done that is irreparable?
gpt
Different components react differently to water. Most ICs, for example, will dry just fine, but may end up with residual water stuck underneath the chip, unable to dry. 

Capacitors can corrode from the inside out, and transistors do weird things when exposed to water, but immediate drying and cleansing with alcohol will usually prevent that. 

Now, the unfixable stuff.

LCD screens are toast in water if water gets between the digitizer and the glass. Also, rechargeable batteries often use alkali or alkaline elements (think lithium ion batteries, among others) that are highly reactive to water. If exposed, very VERY small amounts of water can get into the battery and destroy it, either slowly or immediately. 

Other than that, water with any kind of mineral content can short circuit boards and/or leave deposits that hinder the board's ability to function, and can even cause heat build up. Dropping a phone into distilled water, however, won't do much, except cause a physical mess inside the device. The components themselves would be fine for the most part (except the battery and screen.)