Natural Water Park

Johnson's Shut-Ins State Park is a state-owned, public recreation area covering 8,647 acres (3,499 ha) on the East Fork Black River in Reynolds County, Missouri.

The term "shut-in" refers to a place where the river's breadth is limited by hard rock that is resistant to erosion. In these shut-ins, the river cascades in many rivulets over and around igneous rocks worn smooth over many eons.

It is used by park visitors as a natural water park when the water is not so high as to be dangerous.The bedrock of the area is an erosion resistant rhyolite porphyry and dark colored diabase dikes of Proterozoic age. Waters of the East Fork Black River became confined, or "shut-in," to a narrow channel following fractures and joints within the hard igneous rock. Water-borne sand and gravel cut deeply even into this erosion-resistant rock, carving potholes, chutes and canyon-like gorges.