Clear water is a pretty high resistance, so you'd need a more complex circuit to measure the change in resistance when both your high resistance finger and the water arrived at your chosen level. Also, water will tend to wick up things that are placed into it, so there is a loss of accuracy that way also.
These kinds of measurements are usually made with a float on a sliding rod that either hits switches or rotates a small potentiometer like the gas gauges in fuel tanks. It could be done using a continuity tester that will responde to pretty high resistances and a callibrated rod that you plunge down into your collecting bucket. When the tip of your rod, connected to one contact of the tester, hits the water, to which the other tester lead is hooked somehow, you get current flow and some kind of sound. Then you withdraw the rod to break the surface tension and do it a few more times, measuring the rod's penetration into the bucket several times and take an average. Harder than you think. Tom Fowle
