I have made up a water cooled chamber attached to the back of a large finned heat sink. I did not bother with running any fans across the heatsink, but no doubt I could increase the efficiency if I did so. Using water is more efficient but involves plenty of gear to trip, kick and spill.
I run a simple water pump circulating water through two water inlets to the chamber. The water runs through a couple of metres of copper tubing sitting on the top of the lid of a plastic bucket. This arrnagement dissipates the heat better to the air as opposed to water cooling only in a plastic (insulating) bucket.
I find this arrangement nicely maintains the temperature differential for many hours. The peltier gets super cold and on humid days you can make big ice blocks.
Ted