We worked on a version of thermal fishing bob described here:
We found there were problems with the circuit diagram shown in this wiki page.
This version uses a 10K Thermistor from Ada Fruit:
http://www.adafruit.com/products/372 It comes with a 1% 10K resistor which you can use as calibration or for a resistor divider
Following the excellent Ada Fruit instructions changed the board to stabilize the voltage through the circuit:
Here is the arduino sketch:
We had some successful tests:
The circuit inside its repurposed Kool-Aid enclosure.
We stabilized it with styrofoam cups.
And deployed it in the bathtub.