These old bicycles have not fallen victim to rising sea levels. They have been placed underwater to help seed coral regrowth in tropical waters completely stripped of their natural reefs. Wired up to a solar panel, an electrochemical process coats their metal frames with calcium carbonate from the seawater, creating the perfect surface for coral growth. This new reef, in Pemuteran, Bali, Indonesia, is already attracting fish and other inhabitants.