The World’s Largest Waterfall Is Under the Ocean

You’ve probably heard of Niagara Falls. Maybe even Angel Falls, the tallest one above ground. But what if we told you the world’s largest waterfall isn’t something you can see at all?

In fact, it’s completely underwater.

Hidden beneath the Denmark Strait—between Greenland and Iceland—is a mind-blowing natural phenomenon: the Denmark Strait cataract, a waterfall so massive it makes every land-based cascade look like a gentle stream.

Denmark Strait separates Iceland from Greenland.

Wait, a waterfall under the ocean? How?

This isn’t your typical waterfall tumbling off a cliff. Instead, it’s created by cold, dense water from the Arctic Ocean flowing south, meeting warmer, lighter water from the Atlantic. Because cold water is heavier, it dives below the warmer layer, plunging down the ocean floor like a giant underwater waterfall.

And it’s not just a little slide—this underwater torrent drops an astonishing 3.5 kilometers. That’s more than three times the height of Angel Falls in Venezuela, the tallest waterfall on land.

How powerful is it?

Let’s talk numbers. The Denmark Strait cataract carries more than 123 million cubic feet of water per second—about 50 times the flow of Niagara Falls. And it never stops.

It’s a silent, cold giant: constantly churning, plunging, and driving one of Earth’s most important natural systems—the global ocean conveyor belt (Meridional Overturning Circulation).

Why does this matter?

This underwater waterfall plays a crucial role in regulating Earth’s climate. By helping circulate cold and warm water around the globe, it keeps ocean temperatures stable, supports marine life, and even influences weather patterns. In other words: this invisible waterfall helps keep our planet’s life-support system running smoothly.

But we can’t even see it?

Nope—at least not directly.

Because it’s underwater, the Denmark Strait cataract is invisible to the human eye. But scientists can “see” it using sonar, underwater mapping, and data modeling. Think of it as discovering a mountain or canyon with radar—only this time, it’s a thunderous waterfall hidden in the deep.

Not to Be Confused With…

You may have seen breathtaking aerial photos of what looks like a waterfall tumbling into the sea off the coast of Mauritius. While stunning, that phenomenon is actually an optical illusion—not a real underwater waterfall. The so-called “Mauritius underwater waterfall” is caused by sand and silt being swept off an ocean shelf, combined with light refraction that tricks our eyes. In contrast, the Denmark Strait cataract is a real, physical flow of water—massive volumes of cold, dense Arctic water plunging beneath warmer Atlantic currents, deep beneath the ocean’s surface. One is a visual marvel; the other, a hidden powerhouse of the planet’s climate engine.

Le Morne Brabant mountain with beautiful lagoon and underwater waterfall illusion, Mauritius island

Fun Fact: The Denmark Strait cataract is just one of many secrets the deep sea holds. More than 80% of our oceans remain unexplored.

So next time someone brings up majestic waterfalls, you can drop this surprising truth: the biggest one of all? It’s flowing quietly under the ocean waves.