What happens to an old train once it’s no longer fit for use? In some places, those railcars get a second life at the bottom of the ocean, where they become part of an artificial reef that serves as a habitat for fish and other marine life. This happened recently in Georgia, where two subway cars from Atlanta were added to an existing Atlantic Ocean site called L Reef. The cars were cleaned and then pushed into the water, where they sank to the seafloor, joining a variety of other old railcars, boats, and battle tanks. Coral has since started growing on the new cars, and scientists say they’ve seen several species of fish swimming in the structures. The seafloor along Georgia’s coast is sandy and not well-suited for reef growth, so the repurposed train cars provide a crucial shelter for fish, experts say—while also helping dispose of railcars in a more eco-friendly way. Says Thomas Worthy, former chairman of the Metropolitan Atlanta Rapid Transit Authority Board of Directors: “This seemed like a real, tangible thing we could do to promote sustainability.”