I'll be living on a stretch of my uncle's land this summer, a few miles from the [dirt] road. Way out, no electricity, in a small shack. One of my biggest concerns is refrigeration of meat and milk, and I'm working on a solution that doesn't involve electricity, propane, or ice. I've looked in the the Nigerian Zeer (terra-cotta pots and sand), but I got another idea. If I used an odor-proof sack held under spring water by a system of nets, my meat would stay cold and useable for a week or two. The Loksak Opsak seems like just the kind of thing I could use, but there's one issue. Its description says that it's submersible to 200 feet, but nowhere have I read of this being tested. Can anyone shed any light on this subject here? I've read that the ziplock aspect of the bag is rather loose and only single track, leading me to believe that it might come loose under pressure, thus exposing my meat and milk to the water and so forth.
Can anyone help me out here?

I wouldn't trust it. A real marine drybag would be more like it with a lot of weight in it to keep it down. Some guy tested an Outdoor Research drybag pack with an anchor in it it was still dry after a week.Read lots of reviews from people who do white water.

I don't think an Opsak would work well for you. A bit more elaborate would be to build a spring box [From Kephart, Camping and Woodcraft]

You could probably use a plastic storage bin and a little plumbing to make one. Depending on the geometry of the layout, you might be able to run piping from the spring into the cabin for running water then put the spring box in the cabin.

You'll also have to think about how to keep animals out.
You need to make sure that the temp is cold enough to store meats and leftovers safely.
Cheese, eggs and butter don't need refrigeration and milk doesn't need much.