The Mariana Trench is the deepest point on Earth.
So deep that if you dropped Mount Everest inside,
its peak would still be more than
a kilometer underwater.
So deep that no light reaches the bottom.
And if you could feel it, the pressure would be
about equal to the weight of
48 jumbo jets.
Yet, somehow, life finds a way.
Very weird life.
The truth is, at first glance...
Douglas Bartlett: You wouldn't be very impressed.
It's gonna be this
kind of silky, gray-green sediment.
Narrator: But if you put out some food,
some of the planet's strangest creatures
would emerge from the darkness.
Like these.
They're crustaceans called amphipods.
And some individuals can grow
up to 30 centimeters long,
or about the size of an American football.
Now, like lobsters,
these animals have hard exoskeletons
made of calcium carbonate,
which you normally wouldn't find down here,
more than 10,000 meters down.
Because once you pass 4,500 meters or so,
the pressure is so great
and the temperature is so low
that calcium carbonate dissolves.
But these amphipods have a secret weapon.
Or rather, shield.
The crustaceans are covered
with an armor made of aluminum,
which they synthesize in their bodies,
using aluminum found in the seafloor.
It's a good thing, too,
because those shells are their best defense
against something else lurking in the abyss.
The Mariana snailfish,
aka the deepest fish ever discovered,
which scientists have seen
more than 8,000 meters down.
And there are a lot
of strange things about these fish.
They have flexible bones,
which scientists think helps them withstand pressure.
They're blind, because, well, when it's that dark,
there's no point in seeing.
And...
Bartlett: Their skin is translucent,
so you can see their internal organs.
Narrator: But they're also one of the trench's
top predators.
And if you want proof,
check out this terrifying X-ray image.
Now, snailfish are certainly odd.
But then again, you haven't yet met...
Bartlett: A xenophyophore.
Narrator: It's a single-celled organism
akin to a giant amoeba.
In fact, at about 10 centimeters long,
it's one of the largest
single-celled organisms on Earth.
The trench also has what Bartlett calls...
Bartlett: These little sea pigs.
Narrator: They're small, transparent sea cucumbers
that crawl along the ocean floor
on tentacle-like legs.
But perhaps the most surprising thing you'll discover
inside the Mariana Trench is this:
Plastic.
In 1998, a remotely operated submersible
detected a plastic bag
at 10,898 meters.
And in 2019, an explorer reported
signs of plastic debris even further down.
What's more, researchers have found microplastics
inside the stomachs of amphipods
in the Challenger Deep.
They called it "the deepest record
of microplastic ingestion."
And all that goes to show that even here,
in the most remote place on the planet,
where only four people have ever visited,
there are signs of our vast impact on the world.