The Seas Under Our Oceans

How to keep New York hydrated for the next 800 years.

It’s the late 1950s, and France’s first nuclear submarine, Plongeur, is in deep trouble.

For the last few terrifying minutes, and for wholly mysterious reasons, it’s been in an uncontrollable crash dive.

As the crew look on in horror, the depth gauge spins past 500 metres…then 1,000…then registers they’re two full kilometres down, with the skin of the submarine around them popping and groaning with the building pressure. It wasn’t built for this. It can’t take much more.

Somewhere below them - maybe a thousand metres away, maybe much less - is the sea floor of the Atlantic. They won’t know where until it’s far too late. Impacting it at this speed and depth will be instant death: with a breached hull and vertical kilometres of ocean pressing down upon them, the pressure (anything up to 400 times atmospheric) will crush them quicker than an eye can blink.

4,000 metres. It’ll be any moment now.

…

…5,000?

Impossibly, they’re still alive, and the numbers keep falling.

According to where they think they are, the submersible is now below the depth of the Atlantic at that location. Maybe they’ve somehow been quickly dragged sideways, to somewhere it’s much deeper?

Time passes - and their depth continues to build.

8,500 metres now.

This is absurd. They’re now below the deepest known point in the Atlantic (the Milwaukee Deep), and rapidly approaching a depth exceeding that of any ocean on the planet.

Even more perplexingly, the creaking and groaning has stopped. When they check the pressure upon the hull, it’s lessening - and when they test the water out there, it’s no longer salty. It’s fresh.

Only one utterly fantastical explanation presents itself. Somehow (and honestly who knows how?) they’ve fallen through a crack in the sea floor, into a vast, undiscovered sub-oceanic ocean.

Now their dive quickens, as if they’re caught in a mighty downward current (an underwater waterfall, perhaps?) - and it’s pulling them….where?

If you want to know what happens next, you’ll have to read the rest of Twenty Trillion Leagues Under The Sea by British author Adam Roberts, who is having enormous fun writing some of the most gleefully unhinged yet firmly-scienced speculative fiction being published today.

(I’ll give no spoilers, except that things get particularly bonkers when they’ve passed a depth equivalent to the entire radius of the Earth.)

Sometimes that’s the fun of sci-fi. You read a story & think, “well, that was a madly good knees-up of a thing, and I appreciate the wild imagination of the person who wrote it! But obviously it’s fantasy. There’s zero truth in all this. How could there be?”

Incredibly, it seems this is not one of those times.

In the '60s and '70s, the US Geological Survey reported finding traces of freshwater beneath the sea floor of the east coast of New England, in the United States.

In 2025, a team of scientists went for a proper look at what's down there.

After 3 months, they'd pulled up 50,000 litres (13,200 gallons) of water - some of it drinkable - from hundreds of metres below the sea bed.

Their current working theory based on what they've found, as reported on January 21st by Sascha Pare at LiveScience here:

• There's a gigantic reservoir of fresh water under the sea floor, off the East Coast of the United States…

• The word “gigantic” is barely adequate, because it stretches from New Jersey as far north as Maine, with a volume of trapped water maybe as great as 1,300 km³…

• That amount of water could supply a city the size of New York for 800 years.

GOOD LORD.

The most plausible explanation for this seems to be ancient glaciation.

Sometime between 2.6 million and 11,700 years ago, when the seas were a little (or a lot) lower, freshwater - perhaps melted water from the heat of ice grinding over bedrock - collected underneath the glaciers covering this enormous area.

Then the immense weight of ice above them pressed down with enough force to squeeze this water through a clay-silt layer (known as an aquitard) which would trap it when that mind-boggling pressure was released as the glaciers retreated.

The result: a vast reservoir of water-engorged sediment, hundreds of metres below the sea floor, varying in impurity depending on location, but with some of it on the salty side of potable.

According to a presentation on the website for Expedition 501, the expedition’s international team of scientists predicts there are global reservoirs of offshore freshwater covering as much as [gulp] 500,000 cubic kilometres - which the USGS believes is only a tiny fraction of the water that’s down there at a greater depth, as I previously wrote here:

“Of the freshwater on Earth, much more is stored in the ground than is available in rivers and lakes. More than 2,000,000 mi³ (8,400,000 km³) of freshwater is stored in the Earth, most within one-half mile of the surface.”

Since the United Nations recently announced the world is entering the “era of Global Water Bankruptcy”, requiring immediate international collaboration on a recovery plan, that's pretty hopeful news, if - and it’s a thunderously big “if” - some practical and affordable way to tap these reserves could be cobbled together. I am sure the engineering challenges would be considerable (but well worth tackling).

Here I’m reminded of this arresting graph on global food supplies from Our World In Data, recently shared by Sam Matey-Coste:

(Here’s how they calculated it.)

Since the graph records the state of things in 2022 when red & processed meat still dominated many Western diets (as it still does, of course), how much more hopeful could this graph look in a future graced with the efficiencies of shifting to a more plant-based diet?

I wonder how similar the picture for global water is - how much less it’s down to the absence of the water itself, and more about inadequate infrastructure, shortsighted politics, blinkered capitalism, outdated technology and all those messy but fixable imperfections in the ways humans tend to get things done at scale?

(I’d certainly find that message a lot more inspiring in a newspaper headline than a plain old “the world is running out of water” - which isn’t to say that isn’t happening locally, with dramatic consequences. Just look at what’s happening in Tehran.)

When I mentioned all of this on Bluesky:

Good catch, Other Guy!

“Flood is a 2008 work of hard science fiction by English author Stephen Baxter. It describes a near future world where deep submarine seismic activity leads to seabed fragmentation, and the opening of deep subterranean reservoirs of water. Human civilisation is almost destroyed by the rising inundation, which covers Mount Everest in 2052. Baxter issued a sequel to this work, entitled Ark, in 2009.”

- Wikipedia

When you’re in need of ideas to change the world, maybe it’s a great idea to check in with the science fiction writ- no NOT LIKE THAT…

Anyway! This is a remarkable find, maybe even laying the foundation for a future breakthrough in resupplying the world’s freshwater needs, and I can’t wait to see where it goes.

In the meantime - I wonder how trials are going with this marvel?

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Images: Sarah Lee; Our World In Data; Deborah Diem; ECORD.