"The Shack" is the name of a Christian novel published in 2007 by a former office manager and hotel night clerk. The book sold over 10 million copies by 2009. In the book, the protaganist wrestles with his inner demons and confronts a fictional representation of the Holy Trinity over the course of a weekend in a little shack, after losing his little daughter to a serial killer. It is one of my favorites.
You do not need to enter "The Shack" to find this cache, or wrestle any inner demons. In fact, we recommend you do not try to actually enter the shack at all. The cache is not in there, and the only thing inside the shack appears to be old electrical equipment (none appears to be live, but probably best not to mess with it).
When we hid this cache, we saw hundreds of ducks out here, mostly American Coots with some Northern Shovelers. There were also flocks/pairs of red winged blackbirds, a couple of young hawks, and the occasional blue heron and great egret. Let us know what you see in your log!