This cache is at the entrance (not behind a gate or fence) to the highway 221 tract of Grand Bay. This is a less-used portion of Grand Bay WMA--assumeably because of the scary military signs. I'm here to tell you it's OK to be here according to this site: https://georgiawildlife.com/grand-bay-wma
The actual gate to this portion of the WMA says it is only opened on Saturday and Sunday, so while you can get this cache at any time, if you wish to get them all at one time, you'll need to plan accordingly. The military does shut this area down from time to time for training, and there really isn't anyway to know for sure, so please don't make sure your expectations are set accordingly.
If you do intend to do the rest in the WMA, please be sure to check out the interactive map (with live location for a mobile phone), and please be sure to read the posts for all of the other caches, as one or two of them most likely should not be attempted in a low clearance car.