It says if some great beast opens its mouth ramps, it's watery tentacles around you and pulls you deeper and deeper.

Whoa, that's too scary.

Hey, we're talking sinkholes here.

What secrets do they hide?

Are they as mysterious as they singing?

Let's investigate some of the most famous ones.

Our first stop brings youto a beautiful lake shore surrounded by magnificent green mountains.

Winding road seemed to cut into their natural beauty.

And that's when you see it.

Ah, huge hole gaping in the water with thousands of cubic feet of liquid pouring inside.

No underwater, technically monsters hiding here.

This beast was created by humans.

Welcome to the glory hole off Lake Berryessa.

You'll find the lake in California in the United States.

Oh, it was created by people.

That's not interesting.

You probably thought, Okay, but how about this?

There is a town under the lake.

The small town Monticello was sunk intentionally for creating this lake.

Hundreds of farmers had left there city in the fifties, and all the streets were filled with water a damn named after the town was built near the lake.

When it rains, the water level in the lake rises to prevent it from spilling over the damn edge.

People built a huge spill way more than two school buses across and four times as long as a bowling lane.

To understand better how big the glory hole is.

Imagine you've shrunk to the size of an ant.

Now you're standing on the edge of your bath, watching the water flowing down the bathtub drain and into the sewer.

Similar to that, the water from Lake Berryessa travels through a tunnel and drains into nearby pooed, a creek created to supply the area with drinking and irrigation water.

Monticello Damn serves about 600,000 people.

It also lures hordes of tourists intrigued by the glory hole, which helps the town's economy.

The gaping hole in Lake Berryessa looks scary, but there's nothing extraordinary or mysterious about it once you've had a closer look.

But if you're in search of something, Maur enigmatic, how about traveling down one of the largest underwater holes in the world?

You'll find it in the Caribbean or Caribbean Sea, near the coast of Belize.

It's impossible to miss it.

The thing is a gigantic, bottomless abyss surrounded by coral reefs.

Are you ready?

Our second stop is the great blue hole.

For a long time, people believed it was created by aliens or an ancient civilization.

But how could anyone dig a 40 story deep pit that could swallow the Eiffel Tower?

Another incredible thing about this phenomenon is that the large, dark blue hole is perfectly round.

That's why, despite solid proof, some people still believe it has an artificial origin and when served as storage for something mysterious.

In 1971 famed researcher and traveler Jacques Cousteau went down the sinkhole.

He discovered evidence that the strange, watery pit had been created by nature millions of years ago.

The stalactites structure helped the researcher learn about a powerful earthquake that occurred about 200 million years ago and caused a shift in the tectonic plates.

Later, when the ice began to melt at the end of the Ice Age, the ground collapsed, even Maur and formed a tunnel.

But the pit isn't just a deep, terrifying hole inside, it has many underwater caves where you could easily get lost and get this.

They believe some of these caves, even connect the great blue hole with the mainland of believes.

It's almost like someone created an emergency exit from the continent.

So let's take a dive shall way.

At the start of your descent, you made an array of underwater creatures, different species of turtle sharks, octopuses and more than 60 types of coral.

But the deeper you go, the less crowded against on the pit smooth walls.

You find entrances to dark mazes.

Flooded caves attract you with hanging stalactites and towering stalagmites don't go too far in the oh, you can easily get lost, just like those who disappeared while exploring the Egyptian pyramids.

Better move further to the bottom of the sinkhole about five of those 40 stories down, and you'll need to ditch the diving gear and switched to a submarine, not only because of the pressure, but what awaits you at the bottom.

You've almost made it to the end when you realize you can't see your surroundings anymore.

It's because you're now swimming through a thick layer of hydrogen sulfide, a colorless toxic gas that smells like rotten eggs.

This stuff makes the bottom of the pit totally uninhabitable, and it absorbs sunlight completely Soon you find yourself in complete darkness, but you can do even better.

Your next stop takes you to the Western Pacific with a depth of over 36,000 feet.

It could easily fit the mighty Everest.

Welcome to the Mariana Trench, the deepest point on Earth.

This place will shock anyone not only with its enormous depth but also its inhabitants.

Extremely bizarre creatures have been discovered in the Mariana Trench tiny crawfish fish you can see right through the terrifying goblin shark with its alien like retractable jaw and razor sharp teeth.

And there's the whoa!

What's that?

You see some eerie light moving toward you in the darkness.

Ah, you know this nightmare's creature?

It's the angler fish with its huge mouth that can swallow prey twice its size.

Anyone could instantly recognize that weird fishing pole like dorsal spines protruding above its head.

A comeere.

Yeah, a little closer.

I won't bite more than once.

All this darkness and strange, horrifying inhabitants.

And still the Mariana Trench isn't the most mysterious place in the ocean.

The most enigmatic places, the ocean itself.

Humanity has only explored 5 to 10% of it.

So if we're searching for other civilizations.

Maybe we shouldn't look up at the stars.

Maybe they've been underwater all along.

Wow, this video sure was deep now, isn't it?

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And remember, stay on the bright side of life.