Actually, there're aquarium thermoelectric coolers which are designed based on Peltier Effect. Check out this IceProbe product at this site: http://www.coolworksinc.com/iceprobe.htm
However, Peltier effect cools water best when the volume of water is within an insulated container (i.e. surrounded by insulating material all round of at least 1in thick).
I'm actually thinking how these ThermoElectric Coolers (TECs) can help in making a DIY Chiller that's cheaper and easier maintenance alternative to those... very ex$$$ chillers... Will share any findings IF found...