Why is it that electronics get messed up with water? (I know they short circuit but...read details)?

I know that they get short-circuited by water but when I think about it, that's not a very detailed explination.

Can anyone here gimme like an exact scientific reason why?

Certified A/V tech here.

Pure water by itself will not damage electronics. In fact, deionized water is often used to clean electronic circuits at rebuilding facilities. I have cleaned many, many circuits with water. However, water rarely exists in a pure form and impurities in the water such as minerals, chemicals, food ingredients, etc. can conduct electricity. Soft drinks and coffee are the worst.

If the equipment has a power source attached when it is dunked then impurities in the water can cause current from one circuit to flow through the impure water and into other circuits at random. At this point you will have some malfunction and possibly component failures. If there is no power connected to the item then your chances of recovery are better, however this is not often the case.

To repair a piece of electronics which has gotten wet the contaminants carried in by the water must be removed as quickly as possible, preferably before the circuits dry. Ideally this is done by a tech who disassembles the equipment and flushes it out with a non-water-based solvent, then dries it promptly with hot air. If the contaminants remain inside until the water has evaporated, the contaminants will remain and the circuits will begin to corrode. And a tiny amount of corrosion goes a long way towards disaster in miniaturized electronic equipment.