Somewhere off the Delaware coast, a black sea bass is living inside a 7 train. Not metaphorically.
An actual retired New York City subway car sits on the ocean floor 16 miles off the Delaware coast, one of hundreds resting in about 80 feet of water, coated so thickly in mussels that it’s no longer possible to tell where the old advertising panels used to be.
Divers call the site the underwater train wreck. On official charts it’s listed as Reef Site 11. Everyone else just calls it the Redbird Reef, after the red-painted cars that originally built it.
According to Atlas Obscura, the site holds 714 subway cars, alongside 86 decommissioned tanks, eight tugboats and barges, and roughly 3,000 tons of shredded truck tires, spread across about 1.3 square nautical miles of ocean sand.
None of it would have worked without one specific, unglamorous fact about the local seafloor.
Why the seabed off Delaware needed the help
Jeff Tinsman ran Delaware’s artificial reef program for years, and he never dressed up how bad the underlying geology actually was. Describing the region to CBC’s Day 6 program, he put it bluntly: the mid-Atlantic “kind of got the short end of the habitat stick” when nature was handing out coastline features.
Almost the entire continental shelf here is flat, current-scoured sand, with essentially no natural rock formations to speak of.
That sounds like a minor cosmetic detail, but it matters enormously once you follow how a food chain actually gets assembled from the bottom up. At the base of any productive reef sit filter feeders that stay anchored in one place while pulling food directly out of passing water: blue mussels, barnacles, sponges.
Every one of them needs something solid to physically attach itself to in order to survive. A mussel larva that happens to settle on a loose grain of sand has effectively anchored itself to nothing, and it dies.
The water above Delaware’s coast carries plenty of mussel larvae drifting through it. The sandy bottom below simply offers those larvae nowhere to land.
A retired subway car solves that problem in about the crudest way imaginable. It’s a very large steel box, full of holes.
What the 400-times figure is actually measuring
Mussels colonized the sunken cars almost immediately after deployment. Tinsman told CBC that the carbon-steel Redbird cars held up well under monitoring, offering thousands of square feet of hard surface area to invertebrates that had no way to survive on the bare sand right next to them.
Comparing the resulting encrusted steel directly against the natural seafloor beside it, Delaware’s own monitoring found roughly 400 times as much available food per square foot for fish living on the reef structure compared to the sand around it.
It’s worth being precise about what that figure actually describes. It’s a measure of food density on a given surface area, not a claim that Delaware’s total fish population suddenly multiplied four hundredfold.
Living alongside the mussels are another 30 to 40 invertebrate species, including shrimp, crabs, and worms, exactly the kind of varied menu a black sea bass or a hungry tautog is looking for.
The cars’ doors and windows do additional, practical work here too: the openings let smaller fish slip through easily while forcing larger predators to work around the outside of the structure instead.
New Jersey wanted no part of it
New York City originally offered the retired subway steel for free, with one significant catch: asbestos present in the flooring material of the forty year old cars. Scientific American covered the resulting dispute in 2001, when Clean Ocean Action’s Cindy Zipf pushed hard on the point that nobody had properly studied what asbestos containing material sitting in seawater, covered in growing marine life, would actually do over time.
New Jersey ultimately pulled out of the deal entirely, with then-acting governor Donald DiFrancesco stating the state needed to err on the side of caution for both public safety and the environment. Maryland briefly volunteered to take the cars New Jersey had rejected, then backed out as well.
Delaware said yes to 400 of them and began sinking cars into the Atlantic that August.
Then came the stainless steel, and it went badly
Not every generation of subway car turned out to be equally suited to spending decades underwater. Starting in 2008, the transit authority began offering a newer model, the R32 “Brightliner,” built with corrugated stainless steel skin that everyone involved assumed would easily outlast the older, painted carbon-steel Redbirds by decades.
Instead, the Brightliners lasted only months. Writing in Fast Company, journalist Elissaveta Brandon reported environmental consultant Daniel Sheehy’s diagnosis: the spot-welding process used on the cars created a thin electrochemical layer between two different metals that actively invited corrosion, and the corrugated panel design gave ocean undercurrents something physical to grip onto and gradually peel apart.
New Jersey’s Division of Fish and Wildlife documented the resulting damage in its own 2009 reef program newsletter, reporting that four out of five Brightliner cars surveyed during one dive at the Atlantic City Reef showed significant structural damage, with a separate dive at a different cluster of cars finding essentially the same pattern.
Further deployments of the Brightliner model were suspended entirely. Other states checked their own existing reef sites and found matching wreckage, along with torn sheets of stainless steel that had drifted loose into active commercial fishing trawl nets nearby.
The original carbon-steel Redbirds, built to a much humbler standard, stayed exactly where they’d been dropped, structurally intact.
A question the reef hasn’t actually settled
Marine biologists have spent decades debating a question specific to artificial reefs like this one, often shorthanded as attraction versus production: does a structure like the Redbird Reef genuinely generate new fish biomass, or does it simply concentrate fish that were already spread thinly across a wider area into one easily accessible spot?
A concentrated fish population is easier for anglers to find and catch, which is good news for the local fishing economy and potentially less good news for the broader fish stock if it just redistributes existing pressure rather than adding new fish to the system.
A simulation study published in Ecology and Evolution by Matthew Smith and colleagues argued that attraction effects don’t have to be harmful, and in some circumstances can actually help spread fishing pressure out more evenly rather than concentrating it dangerously in one place. That’s a single modeling study, though, and nowhere close to a settled scientific verdict on the broader question.
Delaware kept expanding the reef regardless of how that debate eventually resolves. The state’s Department of Natural Resources and Environmental Control now describes Reef Site 11 as holding 997 retired subway cars in total, plus a retired cruise ship, decommissioned army tanks, tugboats, a trawler, and two barges. It’s not an unreasonable description to call the whole thing a municipal landfill with unusually good public relations and a genuinely positive ecological outcome attached to it.
Every surviving Brightliner car that hadn’t already been deployed was eventually sent by rail to a scrapyard in Ohio, cut apart for whatever value remained in the specific alloy that had failed it underwater.
The original Redbirds got a considerably better retirement: four decades spent hauling commuters to Flushing, followed by a second, longer career as beachfront property for a growing population of mussels.