Thor's Well is a 20-foot-deep natural sinkhole located on the Oregon coast near Cape Perpetua that appears to drain seawater endlessly. The formation began as a sea cave created by wave erosion until its roof collapsed, creating openings at both top and bottom that fill and drain with the tides. Visitors should maintain a safe distance as sneaker waves and powerful surges around the well have swept people and equipment into the dangerous currents, especially during high tides and storms.