What If the Megalodon Was Hiding in the Mariana Trench?

You’re in the deepest part of our oceans. The Mariana Trench. Suddenly, your sub experiences an earthquake. And when you look outside, you see the terrifying source of it. There is 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.

What could this apex predator be hunting in the deep? How could it withstand the immense pressure? And how would the Mariana Trench make this apex predator more docile?

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 1,000 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 would not 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, its 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 hadal 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.