Re water conductivity. Unlike metals, the resistance of water varies dramatically with the distance between two conductors and hence the volume of water in between. Check this out with a glass of water, with your meter on ohms slowly bring the two probes together. You will see that resistance rapidly reduces from MegaOhms a few inches apart to hundreds of ohms before the probes touch. So where you have very short gaps between circuits on a printed circuit board a drop of water will act as a short.
The actual readings will of course depend upon the purity of your tap water. One thing we can be certain of is that water picked up off a race track surface will undoubtebly be far from pure and will act as a damn good conductor..
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