Last week, I found myself on a 5,000-square-foot barge stuck in shallow water in the middle of the Bronx River. As a tugboat attempted to pull us out, its motor dredged up black sludge, trash, and God knows what else. The air stank of rotten eggs. As Cindy Adams always says, “Only in New York, kids!”

This wasn’t your typical barge, either. It’s an art project called Swale, which was created last year by artist Mary Mattingly as a way to grow produce in a public space. So it was a kind of floating garden filled with edible plants, including apple trees planted atop a 6-foot hill. Anyone can board the barge and pick fresh food for free. Being a barge, it can move, and so I tagged along on a trip from Brooklyn Bridge Park, where it was docked for two months, to Concrete Plant Park in the Bronx.

The idea behind Mattingly’s project is to bring foraging to the concrete jungle, where very little fresh produce is grown locally. Mostly, fresh fruits and vegetables are imported and thus expensive. There’s definitely a market for local food: New York City alone is estimated to have over $600 million worth of unmet annual demand for local food. Swale produces about 400 pounds of food per season, Mattingly says — not enough to satisfy even one person’s fruit and veggie intake in one year. So floating barges are unlikely to meet the local food demands on their own — you’d need an armada — but that’s not Swale’s goal. “We don’t see this as a solution,” says Lindsey Grothkopp, who handles external affairs for Swale. “As an art project, it’s here to just propose new models and new ideas.”

Swale is completely powered by solar panels, and it recycles its own water thanks to a system of pumps and sand filters. It also collects rainwater, and it can desalinate and purify the brackish river water if need be. The barge adds arable land in a dense urban area where land is scarce, and it can float from neighborhood to neighborhood — serving different communities from month to month. Last year, Swale was docked in the Bronx, on Governor’s Island, and then Brooklyn from May to October. (In the winter, it was stored upstate.)

The floating garden is also more accessible than community gardens and rooftop gardens, Mattingly says. On Swale, anyone can board the barge and pick whatever they want, from strawberries and blackberries to kale, lettuce, and chamomile. Most of the city dwellers who visit the floating food forest have never foraged before, says Brittany Gallahan, a college student at the University of Virginia, and Swale’s intern for the summer. They don’t even know where to start. “They’re a little starstruck,” says Gallahan. Whoever is volunteering on board shows them around the garden and gives them some herbs to try in a tea. “They come back with bags and forage,” Gallahan says.

There’s a reason people don’t know how to forage, though: New York City has about 30,000 acres of public parks, but foraging is strictly prohibited by the Parks Department. So most public land in the city can’t be used to grow food. Mattingly launched Swale as a “provocation,” she says: since the barge is floating on water, foraging is allowed there. And it might be working. She’s now partnering with the Parks Department to open the first ever edible garden in a public park in the Bronx, a few feet from where Swale is currently docked. She hopes that the Parks Department will also eventually take over Swale, and keep it docked in the Bronx permanently. That way, she could launch a second barge, doubling the city’s floating farmable area.

For that to happen, though, Mattingly needs money. Like any art project, the barge requires patrons, since it costs $5,000 a month to rent, plus $2,000 a month for insurance. Swale is docking for free, but the overall monthly budget, including rent, insurance, and paying the volunteers who give tours and classes, is about $10,000 a month, Mattingly says. Towing it from place to place costs extra. This year, the barge has been kept afloat mostly thanks to the Parks Department, which helps with rent and pays towing costs. Heineken USA's Strongbow Apple Ciders, which sponsors Swale, also helps with costs, but it’s unclear whether the sponsorship will continue next year — and where the money will come from. “We’re still figuring that out,” Grothkopp says.

For now, Swale is just an art project that is hoping to swing policymakers into growing more food in public spaces. It’s working here in New York City, and when I ask Mattingly if she thinks it could work in other cities in the US, she says yes. Barges could be tweaked to meet the demands of the city hosting them: New York has brackish water, so the garden needs a desalination system. In colder climates, the barge could host a greenhouse. But Boston, Detroit, or Chicago could host a barge only if a rich benefactor could be located to pay for it.

The water has drawbacks, too. After flawlessly floating up the East River — passing by housing projects, high rises, and iconic landmarks like the UN’s headquarters — the barge got stuck in the shallow, stinky waters of the Bronx River. I thought it was going to take hours before we could reach the pier, which was just about 70 feet away. The tugboat — square, skinny, and so tall it looked like a small wave could topple it — dragged the barge backward for a few minutes. Then, dredging up more black sludge, plastic bottles, and cans from the riverbed, it pushed the barge forward again, finally freeing it from the river’s bottom.

When we docked at Concrete Plant Park, the sun was beating down hard. But compared to the concrete pier, Swale’s blueberry bushes, sage, and apple trees provided an island of green. I tried a blackberry from the garden, as well as a bright orange daylily that Gallahan promised me was edible. (There was a little bug inside it, and I ate that, too.) The produce tasted fresh and sweet — if only it didn’t cost so much to grow.