You're in the deepest part
of our oceans.
The Mariana Trench.
Suddenly, you're sub experiences
an earthquake.
And when you look outside,
you see the terrifying source of it.
There's no mistaking
the 15 cm (6 in) teeth
of the largest apex predator,
the megalodon.
Getting bitten by this beast
would feel like being crushed by three
African elephants
stacked on top of each other.
We know more about the surface of Mars
than we do about our oceans.
And with only 15% of our oceans explored,
who's to say no
ancient predators are hiding somewhere
deep underwater?
The deepest part of the Mariana Trench,
Challenger Deep,
stretches 10,984 m (36,037 ft) down.
You could submerge
Mount Everest into it
and still have 2 km (1.3 mi) to spare.
That sounds like
plenty of parking space
for a megalodon or two.
But the Mariana Trench
is a mysterious,
cold and unforgiving world,
steeped in total darkness.
The temperature hovers around
2° C (35.6° F) all year round.
At its worst, the pressure
is 1000 times stronger
than at sea level.
So what if the largest apex predator
never went extinct,
like we thought it did?
What if it adapted to this
hostile environment,
waiting for you to come by
for its dinner?
Two million years ago,
the megalodon was tearing into
the equivalent
of one-and-a-half cows a day.
But this diet plan wouldn't work for this
ancient, warm-water-dwelling
apex predator.
Because sunlight doesn't reach the depth
of the Mariana Trench,
there isn't any photosynthesis.
And no photosynthesis
means not much food.
Animals of the deep sea
often live by scavenging on the decaying
remains of plants and animals
from the upper zones of the ocean.
Larger animals sometimes store food
in expandable stomachs for months.
Others cope by being very small
and needing less food to survive.
So if our megalodon was close
to its pre-historic size,
it would probably
be a few thousand years old.
And it could have the Portuguese dogfish
and the Greenland shark on the menu.
The megalodon would swim to the upper
reaches of the ocean and feed at night.
Then return to the deep during the day.
With a bit of luck,
our hungry megalodon
could even catch some juicy giant squid.
So what's stopping it from chomping
into your puny
10,700 kg (11.8 ton) submarine?
Well, it's teeth and bones
might not be in great shape.
That's because with the intense pressure
of the Mariana Trench,
proteins and calcium start to dissolve
and disintegrate.
The haydel snailfish,
the deepest dwelling fish we know,
has flexible cartilage instead of bones.
All deep-sea creatures
also have molecules called piezolytes.
Their job is to stop the other molecules
from being crushed by the pressure.
The Mariana Trench
megalodon would
most definitely need
to stock up on some of those.
To maintain its body temperature,
our megalodon would
have to be warm-blooded.
And to navigate in total darkness,
it would have to either
become bioluminescent or grow
massive eyes like the giant squid.
Its skin could evolve to enable more
tactile ways of feeling its way around.
An expandable stomach
could help it store food.
And inward-facing teeth could
prevent slimy prey from escaping.
But with so many custom fittings
and edits to its genetic structure,
would it still be
the terrifying megalodon we know?
Most likely not.
So you can plan your trip
to the Mariana Trench
knowing you wouldn't
be eaten by a gigantic shark.
And while you're there,
maybe you'd be up
for a little research project.
Like digging a hole
into the Mariana Trench.
But hey, you know the drill.
That's a story for another WHAT IF.