This cache is hidden in a canyon known as "The Hole in the Ground". It's a popular destination for kayakers and fisherman as Rock Creek that flows through the canyon provides the only public access to Bonnie Lake to the north. There's plenty of parking near the cache location on the side of the road. You're looking for a small bison tube. Watch for rattlesnakes and livestock.
Congrats to Nuttyguy for the FTF!