The ocean is getting cleaner. No one knows why.

Ghost nets are disappearing. Marine debris is vanishing from coastlines. Industrial fishing crews are hauling up empty nets—cut open by something powerful enough to tear through equipment built to hold tons.

At first, Dr. Mara Keating thinks the impossible might be good news.

A marine systems ecologist who studies what humanity leaves behind in the ocean, Mara begins tracking the disappearances across unrelated datasets. What she finds makes no sense.

The ocean isn't simply getting cleaner.

Something is sorting it.

Useful materials are disappearing first. Lost equipment is being opened, stripped and moved. Objects are traveling against currents. And across thousands of miles of Pacific seafloor, the evidence points in one direction.

Toward one of the deepest places on Earth.

When a research expedition discovers an enormous structure where nothing existed less than a year earlier, the question is no longer what is happening to the ocean.

It's who is doing it.

And what they're building beneath us.

THALASSA: Something Beneath Us is a cinematic first-contact science-fiction thriller about intelligence, evolution, and the terrifying moment humanity realizes it may not be Earth's only civilization.