I'm not totally sure what your application is, but if all you want to do is visually monitor the temperature, you might see if your school has any CBLs lying around that you can use. The CBL is a device that plugs into most any TI graphing calculator, and comes standard with sensors for light, voltage, and temperature. The nice thing about this is that it won't cost you anything, and the application for 83+/84+ is graphically very nice. In addition, it is capable of doing data logging over time. Also, I'm almost certain that the temperature probe is waterproof.
Alternatively, you might consider picking up one of
these. Jameco carries them for $0.34 a piece. This has an analog output that you can feed into a robot controller, or just monitor with a voltmeter. Since it is just a TO-92 case (like a small transistor), you will need to find some way to electrically insulate it, to protect it from the liquid.
I suspect that you'll find either of these solutions to be much more cost-effective and easier to use than the product in Andy's link.