Scientists conducting a first-of-its-kind drilling operation have extracted samples of fresh water hiding in massive reservoirs deep under the ocean.

Their consortium of more than a dozen nations sank pipes through the seabed muck off Cape Cod this summer to extract water and sediments.

The samples will be studied to see how old that water is, what organisms live in it and whether it is a renewable resource that could someday slake the planet’s growing thirst.

The scientific expedition was launched nearly 50 years after U.S. researchers searching for hydrocarbons and minerals discovered freshened water under the seabed.

"One of the last places you would probably look for fresh water on Earth is beneath the ocean, which is full of salt. So, that is sort of a mystery in itself," said Brandon Dugan, the expedition's co-chief scientist who spent 20 years preparing for the mission.

The research work at sea unfolded over three months from Liftboat Robert, an oceangoing vessel that, once on site, lowers three enormous pillars to the seafloor and squats above the waves.

The vessel normally services offshore petroleum sites and wind farms.

“We're currently about 25 to 30 miles ( 40 to 48 kilometers) off the coastline. We have about 160 feet (49 meters) of water beneath us. And then we're drilling down another 300 feet (91 meters), and we're starting to see water that doesn't look like an ocean. It has much less salt than the ocean, almost to the definition of fresh water – so, one part per thousand salt we've discovered," Dugan said aboard L/B Robert.

It's just one of many depositories of “secret fresh water” known to exist in shallow salt waters around the world that might some day be tapped to slake the planet’s intensifying thirst, Dugan said.

Expedition 501 extracted thousands of samples from what is now thought to be a massive, hidden aquifer stretching from New Jersey as far north as Maine.

Scientists will be analyzing nearly 50,000 liters of the freshened water back in their labs around the world in the coming months.

The global expedition seeks to answer questions on the origins of this undersea treasure.

"One of the ideas is 20,000 years ago, there was a large ice sheet above us and that ice sheet was melting at the bottom and it pushed that freshwater down beneath the continental shelf. Then sea level rose when those glaciers melted and trapped all that freshwater. That's a hypothesis that we're going to be able to test with some of our techniques,” Dugan said during a sunset interview with the Associated Press.

“Another hypothesis is in the geological past, sea levels have been lower, 300 feet (91 meters) lower. Instead of having 150 feet (46 meters) of water beneath us, this was a beach. And we just had rainwater coming down and seeping into the ground, just like you would in your backyard today. But now it's been flooded by the ocean," he said.

Dugan has spent hours watching the drilling crew pull out pipes from the seabed, wondering what secrets the latest samples may reveal.

Fellow researchers and support crew are not surprised to see him dipping his fingers into the undersea sediment and rolling his thumb and index finger over it slowly to test the texture.

"The two most surprising things that we've seen here are one, that the shallow ... the freshened water is starting at a much shallower depth than we had originally anticipated and ending deeper than we'd originally anticipated, indicating that there's probably more freshened water here than we thought two months ago before we started this expedition,” Dugan said.

“Another interesting thing that we’ve seen is everything that we're drilling through – rocks that are tens of millions of years old – are still loose sediments like beach sand and clay that you would buy at a modeling store. And so, why haven't these turned into rocks? This might be part of the fluid flow story that explains this freshened water system," he said.

The potential for the water is enormous.

So are the hurdles of getting the water out and puzzling over who owns it, who uses it and how to extract it without undue harm to nature.

It's bound to take years to bring that water ashore for public use in a big way, if it's even feasible.

Why try?

In just five years, the U.N. says, the global demand for fresh water will exceed supplies by 40%.

Rising sea levels from the warming climate are souring coastal freshwater sources while data centers that power AI and cloud computing are consuming water at an insatiable rate.

The fabled Ancient Mariner’s lament, “Water, water, every where, nor any drop to drink,” looms as a warning to landlubbers as well as to sailors on salty seas.

In Virginia alone, a quarter of all power produced in the state goes to data centers, a share expected to nearly double in five years.

By some estimates, each midsize data center consumes as much water as 1,000 households.

Each of the Great Lakes states has experienced groundwater shortages.

Cape Town, South Africa, came perilously close to running out of fresh water for its nearly 5 million people in 2018 during an epic, three-year drought.

South Africa is thought to have a coastal undersea freshwater bonanza, too, and there is at least anecdotal evidence that every continent may have the same.

Canada's Prince Edward Island, Hawaii and Jakarta, Indonesia, are among places where stressed freshwater supplies coexist with prospective aquifers under the ocean.

Enter Expedition 501, a $25 million scientific collaboration of more than a dozen countries backed by the U.S. government's National Science Foundation and the European Consortium for Ocean Research Drilling.

Scientists found fresh or nearly fresh water at both higher and lower depths below the seafloor than they anticipated, suggesting a larger supply even than that.

Scientist worked in shifts in a round-the-clock operation, with the drilling crew extracting samples and researchers logging, packaging it and processing the material.

Jez Everest orchestrated the intricate operation as Expedition 501 project manager.

Expedition 501 was quite literally groundbreaking – it penetrated Earth below the sea by as many as 1,289 feet or nearly 400 meters.

But it followed a 2015 research project that mapped contours of an aquifer remotely, using electromagnetic technology, and roughly estimated salinity of the water underneath.

That mission, by the Woods Hole Oceanographic Institution and Lamont-Doherty Earth Observatory at Columbia University, reported evidence of a “massive offshore aquifer system” in this area, possibly rivalling the size of America’s largest – the Ogallala aquifer, which supplies water to parts of eight Great Plains states.

Two developments in 1976 had stirred interest in searching for undersea freshwater.

In the middle of Nantucket Island, the U.S. Geological Survey drilled a test well to see how far down the groundwater went.

It extracted fresh water from such great depths that it made scientists wonder if the water came from the sea, not the sky.

The same year, that federal agency mounted a 60-day expedition aboard the drilling vessel Glomar Conception along a vast stretch of the Continental Shelf from Georgia to Georges Bank, off New England.

It drilled cores in search of the sub-seabed's resources, like methane.

It found an eye-opening amount of fresh or freshened water in borehole after borehole.

That set the stage for the water-seekers to do their work a half century later.

"So what we're learning here in New England this summer, we can apply to other areas like South Africa, Indonesia, Japan, Australia, and even Antarctica to put this understanding in a global context, which is really important when you think about by 2030, 60% of the world's population won't have continuous access to fresh water," Dugan said.

Rob Evans is a Woods Hole Oceanographic Institution geophysicist whose work off Martha’s Vineyard and New Jersey in 2015 helped guide the current expedition.

"We have to be really careful about trying to understand and think about exploiting these kinds of resources because we just don't understand enough about what the impacts of doing that would be to our main onshore supplies. If we were to start pumping, for instance, is it an isolated body? If it is, then once it's tapped and drained, then it's gone, right?" Evans said from his office on Cape Cod.

Evans 2015 work involved towing an electromagnetic transmitter and receivers behind a ship to detect the presence of freshwater under the sea floor.

For most in the project, getting to and from Liftboat Robert meant a voyage of seven hours or more from Fall River, Massachusetts, on a supply boat that made round trips every 10 days or so to replenish stocks and rotate people.

On the platform, around the clock, the racket of metal bore pipes and machinery, the drilling grime and the speckled mud mingled with the quieter, cleaner work of scientists in trailers converted to pristine labs and processing posts.

There, samples were treated according to the varying needs of the expedition’s geologists, geochemists, hydrologists, microbiologists, sedimentologists and more.

Passing through clear plastic tubes, muck was sliced into disks like hockey pucks.

Machines squeezed water out.

Some samples were kept sealed to enable study of ancient gases dissolved in the water.

Other samples were frozen, filtered or left as is, depending on the purpose.

After six months of lab analysis, all the science teams of Expedition 501 will meet again – this time in Germany for a month of collaborative research that is expected to produce initial findings that point to the age and origin of the water.

On July 31, Liftboat Robert cranked up its legs from this place of hidden water to end a mission that lent credence to another passage from “The Rime of the Ancient Mariner," Samuel Taylor Coleridge's classic poem about life, death and mysteries at sea.

In a prelude to the poem, in some editions, Coleridge wrote: "I readily believe that there are more invisible than visible Natures in the universe.”

AP Video shot by Rodrique Ngowi.