If you think subway cars are only useful so long as they are efficiently carrying urban travelers from point A to point B, well, you’re wrong!

It turns out that hundreds of retired New York City subway cars have been finding a second home—80 feet underwater, and 16 nautical miles off the coast of Delaware. There they are helping to transform “a barren stretch of ocean floor into a bountiful oasis, carpeted in sea grasses, walled thick with blue mussels and sponges, and teeming with black sea bass and tautog.” So far, 666 subway cars have already made their way to the ocean floor, and the results have been impressive: “a 400-fold increase in the amount of marine food per square foot in the last seven years,” and “In the last several years, the reefs have drawn swift open-ocean fish, like tuna and mackerel, that use the reefs as hunting grounds for smaller prey. Sea bass like to live inside the cars, while large flounder lie in the silt that settles on top of the cars.” This is great news, as ocean acidification from climate change and other human disruptions are harming reefs around the world.