(CNN) If you dive deep enough off America's northeast coast you'll find something surprising under the Atlantic Ocean: freshwater.

A gigantic aquifer of mostly freshwater, hugging the coastline from New Jersey up to Massachusetts, sits below the ocean floor. It contains at least 2,800 cubic kilometers (that's about 739 trillion gallons) of liquid. That's enough water to fill 1.1 billion Olympic-sized swimming pools.

It's the biggest known undersea, freshwater aquifer on Earth. But more importantly, there may be other such freshwater aquifers like it throughout the world, a potentially huge natural resource on a planet with a steadily growing population.

The discovery was made by researchers from Columbia University and the Woods Hole Oceanographic Institution while they were doing a survey of the sea floor off the US northeast coast, according to the study, published last week in the journal Scientific Reports

Since at least the 1970s, companies in the region drilling for oil on the sea floor would sometimes hit pockets of fresh water, but it was unclear as to how much water was down there.

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