When the roof over a subterranean river collapsed and exposed the water to the open surface, a macabre window opened up which is known as the Devil’s Den! The Devil's Den is privately owned and operated as a scuba diving training and recreational facility. The temperature is a pleasant 72 degrees year round which means you'll have a comfortable dive. Why is a place of such beauty called the Devil's Den? Because on a cold winter morning you can see steam rising like smoke from the cave's chimney. Early settlers named it the Devil's Den. The Devil's Den is opened to scuba divers and snorkelers only. No swimmers or casual visitors, no children under 6 years old, and no pets allowed.