It’s a strange feeling to be standing in the mud 40 feet below the East River without getting wet. Even stranger is having a 119-foot-tall ship above your head, its 12,000 tons balanced out on a few concrete blocks around you. So it goes every day in the dry docks of the GMD Shipyard, Brooklyn’s last ship repair facility.

Over the past decade, Brooklyn’s industrial waterfront has slowly been erased, with residential towers replacing sugar refineries, oil depots, and piers. But at the GMD Shipyard Corp., business is booming. During a recent visit to this facility, located inside the Brooklyn Navy Yard campus, its three dry docks were filled to capacity with an array of barges, ferries, and ships, keeping its 150 employees working nonstop.

Inside historic Dry Dock 1, a New York City landmark that has been in service since 1850, two small barges were being prepped for repairs, while in the enormous graving docks of Dry Docks 5 and 6, workers were sandblasting a training ship and painting a local ferry.

Up and down the coast of the East River, the last vestiges of the working waterfront are disappearing, but down in the GMD Shipyard, it is clear that the Port of New York and New Jersey is still an important destination.

Not all that long ago, Brooklyn’s waterfront was lined with a wealth of shipyards, dry docks, piers, and other maritime support facilities. “When I first got into this, there were ship docks all around Brooklyn. There were coffee piers, there were banana piers, and ships constantly coming and going out of the harbor,” says Michael Sanborn, the general manager of the GMD Shipyard, who started working on the waterfront in 1984 as a machinist apprentice in Red Hook. “In the late ’80s, I could probably name 25 shipyards in the area. But now, there’s maybe half a dozen.”

After the demolition of Red Hook’s Todd Shipyard in 2006, where the graving dock was filled in to create an Ikea parking lot, the GMD Shipyard became the last remaining dry dock facility in Brooklyn. Today, it is one of just a handful of marine maintenance businesses in New York City, including the 115-year-old Caddell Dry Dock and Repair Company in Staten Island, which operates seven floating dry docks on the Kill Van Kull.

In the Port of New York and New Jersey, which is “the third largest port in the United States,” there are only a few large dry dock facilities still open for business, and the changing waterfront may soon claim another victim. The future of the century-old Union Dry Dock in Hoboken, New Jersey, is now being debated, with the city’s mayor advocating for expanded city parkland, and NJ Transit and NY Waterway hoping to create a much-needed ferry repair facility.

As more and more residents move to the post-industrial shorelines of the East River and the Hudson River, the demand for waterfront property has skyrocketed. “The real estate value has closed up a lot of the repairing people,” says Sanborn. “The dry dock companies close up, and the high-rises go up.” These changes are visible just next door to the GMD Shipyard, where a new 17-story WeWork office is being completed on a narrow strip of land at Dock 72.

Despite the current building boom happening on the region’s waterfront, the future of the New York harbor—and the GMD Shipyard—will increasingly be shaped by storms and sea level rise. This was made clear during a recent conference organized by The Brooklyn Waterfront Research Center (BWRC), titled Brooklyn Waters: Sea Level Rise, Sustainability, and Resilience Along the Brooklyn Waterfront. Throughout a day of panels and presentations, a host of scientists, engineers, and architects spoke out about the difficult challenges that New York City will soon face, with sea levels expected to rise up to six feet (or more) by the end of this century.

The facilities of the GMD Shipyard, which are essentially located in and below the East River, are at the front line of these coming changes. The shipyard got a glimpse of the future during Hurricane Sandy, when an enormous storm surge pushed up the East River and into the Brooklyn Navy Yard. “We lost most of the electrical infrastructure in the place. Every pump and motor that runs the dry docks was lost,” remembers Sanborn. “The water was four or five feet above the dry dock. It was just water everywhere.”

“The dry dock companies close up, and the high-rises go up.”

The Brooklyn Navy Yard suffered almost $100 million of infrastructural damage during Hurricane Sandy, and is now working towards a more comprehensive plan for future floods. “There is no way there won’t be another Hurricane Sandy. There is no way we are not going to end up underwater again,” Clare Newman, the executive vice president of the Brooklyn Navy Yard Development Corporation (BNYDC), said during a presentation at the recent BWRC conference. And yet, she noted, “there is no way to dry-proof the Navy Yard.”

“What we want to do over the next couple years is to go building by building, starting with the most vulnerable … and think about how can we best make that individual building and the businesses within it more resilient to a storm,” said Newman. “There are certain parts along the waterfront in the yard where we have thought about doing berming, mostly to mitigate any wave action impact, but the focus for us is really about making sure that the businesses and all of their valuable equipment come up out of the floodplain.”

At the GMD Shipyard, storms surges and real estate pressure are all part of doing business on the waterfront, and work will continue in the dry docks much as it has for the past 168 years, no matter what the future brings. “We’ve been through a lot of nor’easters, which weren’t as bad as Sandy, but we’ve seen water rush in here. You prepare for it as best you can and keep going right after it,” says Sanborn. “It’s a beautiful place to work, and it’s very busy, so that helps.”

Dry Dock 1, which was declared a city Landmark in 1975, was constructed between 1840 and 1851, at a cost of over $2 million at the time. During its early years, the dry dock helped service the USS Monitor.

The dry dock is now operated by the GMD Shipyard Corp., which began leasing space from the Brooklyn Navy Yard Development Corporation in 1986. In its early years, GMD focused exclusively on repairing Navy vessels.

After bringing in a new boat for repairs, Dry Dock 1 is drained by pumping its water out into the Wallabout Bay. There are six dry docks located inside the Navy Yard, but only three are currently active.

The two larger dry docks operated by the GMD Shipyard Corp. are located just up the coastline of the bay, and are situated adjacent to the Brooklyn Navy Yard’s newest addition, a 17-story office building located at Dock 72.

This new office tower, which topped out last October, will house a 220,000-square-foot WeWork facility. It’s built out onto a narrow dock located between Dry Docks 2 and 3, which are controlled by the BNYDC, and currently flooded and inactive.

When completed, the WeWork offices will look out onto the active ship repairing facilities in Dry Docks 5 amd 6. The GMD Shipyard will make for an interesting neighbor: Its iconic cranes can operate 24/7, as workers sandblast, weld, and paint ships.

Inside Dry Dock 5, a barge, ship, and ferry all fit in for repairs at once. This impressive structure is 1,092 feet long and 150 feet wide. In its earlier years, the Brooklyn Navy Yard was an important ship building facility—the USS Ohio was built and launched here in the 1820s.

At the head of each dry dock is a hollow structure called a caisson, which is floated into position and used to seal off the graving dock from the East River. “The caissons are replaceable parts. They are like ships,” notes Sanborn. “They are 50 feet high, 150 feet wide, and about 12 feet in thickness.”

Standing inside the dry dock, it can be disconcerting to think that this hollow, floating structure is all that holds the seawater back. “They are actually like a floating vessel; once we pump the water out, they become buoyant,” explains Sanborn.

In the hollow core of the caisson, a series of gangways and ladders lead down to the lower levels. Each caisson has its own pump station inside to remove water.

The lower depths of the caisson have been flooded with water to settle it into place. “You could compare them to a sailboat, because they have a concrete bottom to keep them buoyant. Otherwise, they would just flip over,” says Sanborn.

The docks of the shipyard are lined with a system of enormous cranes that have the capacity to lift 15 to 200 tons. The cranes can be used to lower the dry dock blocks down into the graving docks. These concrete blocks weigh three to five tons, and are used to support ships when water is pumped out of the dry dock.

A series of warehouses and workspaces also line the docks, which house the yard’s machine shop, pipe shop, and other facilities. “We have around 150 employees of all different trades,” says Sanborn, including ironworkers, fitters and welders, carpenters, line handlers, and machinists. “It’s just about full time, as long as we are keeping busy.”

The carpentry shop, surrounded by wooden shims, which used to help support ships resting on the dry dock blocks. During World War II, the Brooklyn Navy Yard was “the world’s busiest shipyard,” according to Turnstile Tours, the yard’s official tour company, and 70,000 workers were employed here “building battleships and aircraft carriers, repairing over 5,000 ships.”

After World War II, New York City continued to be a hub for boat building and repair. “More than 40,000 people still worked in the city’s shipyards in 1960,” according to the New York Times. However, during the 1970s, the industrial waterfront and the newly decommissioned Brooklyn Navy Yard entered into a long period of decline.

At Dry Dock 6, a 540-foot-long training ship barely takes up half the space. This dock is also 1,092 feet long and 150 feet wide. It is difficult to gain a sense of perspective, but this former cargo ship is 119 feet tall, while the dry dock is 50 feet tall.

Down inside the dry dock, the ship looms high overhead. Despite the limited number of shipyards now remaining in the New York City area, competition for clients is fierce. “We don’t have a monopoly on it, that’s for sure,” says Sanborn. “There is competition out there, and we compete for everything that’s in here.”

Regular inspections, maintenance, and repairs are required for most ships on the water today, leading to a steady stream of customers. “Most of the vessels you see out there that are doing any kind of commercial work are regulated, and they have to get into a dry dock facility every two years to 30 months,” says Sanborn.

Although it seems precarious, the entire weight of this 12,892-ton vessel is supported by a carefully arranged set of dry dock blocks. “Our barges are a little bit easier to dock, because they are square and flat,” explains Sanborn. “Our Coast Guard vessels and our ships are a little bit more difficult.”

Down underneath this 11-storyl ship. “The blocks are concrete, and they have wood caps,” explains Sanborn. “The wood caps are to protect the vessel, so it’s not just steel sitting on the concrete.”

A set of blocks waiting for the next customer, as sand blasting debris are cleared away. “It’s been very busy, which is good. The busier we are, the more efficient we are,” says Sanborn. “We go through peaks and valleys. I’ve been in this industry for a long time, and we are sort of waiting for it to drop out again. We hope it doesn’t.”

Nathan Kensinger is a photographer, filmmaker, and curator who has been documenting New York City’s abandoned edges, endangered neighborhoods, and post-industrial waterfront for more than a decade. His Camera Obscura photo essays have appeared on Curbed since 2012. His photographs have been exhibited by the Museum of the City of New York, the Queens Museum, the Brooklyn Museum, the NYC Parks Department, and inside the Atlantic Ave-Barclays Center subway station.