Jacob’s Well is a significant karstic spring, the largest perennial spring in the Texas Hill Country. It flows from the most extensive underwater cave in Texas, opening in the bed of Cypress Creek, a few miles north of Wimberley, Texas.The twelve foot (four meter) diameter mouth of the cave serves as a popular swimming and water recreation spot for the local land owners whose properties adjoin Cypress Creek. From the opening in the creek bed, Jacob’s Well descends vertically for about thirty feet (ten meters), continuing from there at an angle as a series of chambers separated by narrow, often deeply silted and unstable necks, ultimately reaching a depth of at least one hundred and twenty feet (forty meters).
From the dawn of recorded history until the modern era, the Trinity Aquifer-fed natural artesian spring gushed water from the mouth of the cave and as much as thirty feet (ten meters) into the air.
With the decrease in water flow through the submarine cave system, divers were for the first time able to descend to the first chambers. Jacob’s Well has the notoriety of being one of the most dangerous underwater caves for SCUBA divers.
At least eight divers have lost their lives while exploring Jacob’s Well. At least four chambers have been explored, the last of which requires passage through a neck barely large enough for a diver to fit with his air tanks.