Monsters From the Depths: 5 Truly Terrifying Sea Creatures
By: Sajjad Choudhury
Tags: History, Nature, Oceans, Prehistory, Science

Monsters From the Depths: 5 Truly Terrifying Sea Creatures

Credits: Roger Harris / Image Source

The ocean has always been a dark and mysterious place. Even today, with all of our technology, more than 80% of the ocean has never been mapped, explored, or seen by humans. New species are discovered every year, and there’s no way of knowing what really lurks beneath the depths.

There could be an ancient sea monster so elusive that we would never know it existed. Frightening thought, right?

Luckily for us, although there are giants like blue whales and colossal squid, they’re relatively harmless to us humans and wouldn’t compare to the sheer monstrosities that stalked the waves long ago.

Of all the sea creatures that have ever existed on Earth, five, in particular, stand out as being truly terrifying. Although they went extinct millions of years ago, they still live on in our imagination today.

1. Megalodon

An estimation of how big the megalodon would’ve been compared to a human | Image sourced from Wikimedia Commons

The megalodon is probably one of the most iconic sea monsters of all time. It was a giant shark the size of a school bus and lived between 23 million to 3.5 million years ago. It’s been estimated that some may have also survived as long as 1.5 million years ago, which would’ve put them into contact with our early ancestors!

They could grow as long as 14–20 metres (47–67ft) in length, making them bigger than a school bus, and their maximum weight would’ve been ten times heavier than that of an African elephant. Over 70 tonnes!

However, while size may be one thing, what made them truly terrifying was their teeth. They had 276 sharp serrated teeth that were ideal for ripping flesh apart. While a human has a bite force of around 1,317 newtons, the megalodon likely had a bite force between 108,514 and 182,201 newtons! That’s over 100 times more powerful and more than enough to chew through steel.

So how effectively did they use these teeth? Well, for comparison, great white sharks today target their prey’s soft undersides, but what would a megalodon do?

Well, it wouldn’t care about how armoured you were or how thick your skin was. It would go straight for your chest cavity and puncture your heart and lungs with its powerful jaws. Of course, that was effective because most of its prey were whales and large seals who had little to no protection except for their blubber. If a megalodon encountered a human, it would’ve been able to snap your body in two without any effort at all!

Unfortunately, the megalodon went extinct due to cooling sea temperatures and competition from other predators. They needed warm waters for breeding, and the drop in temperature also affected the availability of food. As whales and other sea creatures evolved to become smaller, the megalodon couldn’t keep up and soon vanished from existence.

2. Liopleurodon

A liopleurodon ambushing its prey — Image Source

The Liopleurodon (meaning smooth-sided teeth) was a large marine reptile that lived between 166 to 155 million years ago during the age of the dinosaurs.

It could grow to more than six metres (20ft) in length, and while that may not sound particularly big, their pointy head made up a full fifth of that, and here’s where the scary part comes in.

They had forward-facing nostrils on their snout, meaning that they could smell prey from a great distance. If you happened to be in range, they would’ve quickly accelerated towards you with their powerful flippers and swallow you whole! Still, it’s probably better that they didn’t chew you to pieces with their powerful jaws, known to have been even stronger than that of a T-rex.

You wouldn’t even be able to escape out of the water because the liopleurodon did not have gills, but lungs meaning it had to make frequent trips to the surface to breathe. Scientists don’t know whether it could leap out of the water like a crocodile, but if you had been around to see one, you probably wouldn’t want to test the theory out.

Unfortunately, like all giant carnivores, the liopleurodon went extinct about 150 million years ago when a more vicious type of marine reptile emerged. These were called the mosasaurs, and they were sleeker and more adapted for hunting the same prey. The liopleurodon simply couldn’t compete any longer and slowly died out.

3. Mosasaurus

A representation of a mosasaur — Sourced from Wikimedia Commons

The name of the mosasaurs means ‘lizard of the Meuse river’, and it lived between 82 and 66 million years ago across much of the early Atlantic ocean.

They were absolute monsters, weighing up to 28 tons, measuring 16 metres (55 ft), and devouring literally anything that swam near them, including plesiosaurs and great white sharks. They were such ruthless hunters that they would even hunt other smaller mosasaurs. Fossils appear to indicate that even the largest species were at risk of being predated, so it’s no wonder that they wiped out the smaller but equally ferocious liopleurodon.

It’s thought that they hunted in very deep waters but wouldn’t travel far from the shore because, like most marine reptiles, they needed to surface for air. However, they were highly adaptable, and their tails changed over time to help them propel through the water more easily.

If it weren’t for the asteroid that wiped out the majority of marine life, they would’ve survived for much longer. Unfortunately, due to their sheer size, they needed to eat large amounts of food, which simply wasn’t available anymore. So, like most creatures of the time, they too died out and were eventually replaced by crocodiles, who became the new apex predator.

4. Godzilla Shark

A group of Godzilla sharks — Image Source

This monster shark was only recently discovered in 2013. Palaeontologists uncovered a bizarrely well preserved two metre (6.7 ft) long fossilised skeleton in New Mexico and noted that it had twelve rows of piercing teeth and, more frightening, a pair of fin spines on its back.

Though only small compared to other mega predators, it was the largest preserved fossil and may have been a link with fish and reptiles thanks to its unusual spines.

The Godzilla shark lived 300 million years ago, and likely remained at the bottom of ancient lagoon estuaries, using its teeth to crush prey like crustaceans and small vertebrates.

Though its teeth were nowhere near as large as other predators, only being around 2cm long (under an inch), its recent discovery and name alone make it worthy of reaching a spot on the rankings.

5. Livyatan

Image sourced from Wikimedia Commons

Think back to the megalodon and how fearsome it was. You wouldn’t expect it to have much competition, right? Well, it did, and the Livyatan was just that, a fearsome predator in its own right and one that competed with the megalodon. It was so terrifying that it was named after the Leviathan, the giant sea monster from the Bible.

Livyatan Melvillei was a ‘hyper carnivore’ and an apex predator. Although it was a whale, like today’s orcas, it preyed on other whales, seals, and anything that could fit into its mouth.

It was as large as a sperm whale and could grow up to 17.5 metres (57 ft), making it one of the largest predators to have existed since the dinosaurs. What makes this whale truly terrifying, though, was its teeth. Each one could grow to 36cm (1.2 ft), making them the largest biting teeth of any known animal, excluding elephant tusks.

These whales lived in the same oceans as the megalodons and fed on the same prey, so frequent clashes would’ve been inevitable.

The Livyatan’s skull alone was three metres (9.8 ft) in length and could do some serious damage thanks to its strong temporal muscles. Nothing would’ve been able to get in the way of this beast.

Except, of course, as you might’ve guessed, climate change. Even the mightiest of sea monsters could not escape the wrath of cooling oceans. Sadly for the Livyatan, it went extinct between 12 and 13 million years ago, around the same time as when its favourite prey also succumbed to the changing climate.