Mega-SLOW-don! The Meg could only swim at 1.2mph (five times slower than Michael Phelps!)

The Meg movie franchise sees the megalodon shark portrayed as a giant, monstrous beast that can race through the water towards unsuspecting victims.

But a new study shows that while the megalodon was big – up to 20 meters long – it wasn’t exactly fast.

While previous estimates suggested the megalodon could swim at 5 km/h, researchers now believe its top speed was more like 2 km/h.

By comparison, Olympic legend Michael Phelps clocked speeds of about 6 mph in his prime.

‘Megalodon [was] an “average swimmer” with occasional bursts of swimming faster to catch prey,’ said Professor Kenshu Shimada, lead author from DePaul University in Chigaco, USA.

While previous estimates suggested megalodon could swim at 5 km/h, researchers now believe its top speed was more like 2 km/h

The megalodon, meaning big teeth, roamed the oceans between 15 and 3.6 million years ago and is widely regarded as one of the largest and most powerful predators in history.

Experts believe the monster looked like a beefier version of the now-feared great white shark and weighed up to 100 tons.

In their new study, the team sought to understand the creature’s fastest swimming speed.

While previous studies focused on megalodon’s teeth, the researchers turned instead to placoid scales — tiny megalodon scales found in rocky outcrops in Japan.

“Our big scientific findings come from ‘little evidence’ as small as grains of sand,” said Professor Shimada.

Their analysis revealed that megalodon was not an active fast swimmer despite its massive size.

The placoid scales showed that the creature was not equipped with “keels” – narrow ridges characteristic of fast-swimming sharks.

By comparison, Olympic legend Michael Phelps (pictured) clocked speeds of about 6 mph in his prime

While previous studies focused on megalodon’s teeth, the researchers turned instead to placoid scales — tiny megalodon scales found in rocky outcrops in Japan

However, this finding was surprising to the scientists, who had recently discovered that megalodon was warm-blooded.

“The question was how the fossil shark consumed the high level of metabolic heat resulting from its warm-bloodedness without being an active swimmer,” the team explained in a statement.

The researchers turned to previous studies and discovered another possible function for megalodon’s warm-bloodedness.

Essentially, the ancient shark was greedy, according to the experts.

“It suddenly made perfect sense,” Professor Shimada said.

“Otodus megalodon must have swallowed large chunks of food, so it is quite possible that the fossil shark reached gigantism to invest its endothermic metabolism to aid visceral food processing.”

The extinct beast from below: Megalodon roamed the seas more than 3.6 million years ago

In the photo: Megalodon

The megalodon, which means big tooth, lived between 23 and 3.6 million years ago.

O. megalodon is considered one of the largest and most powerful predators in vertebrate history, and fossil remains suggest it grew up to 20 meters in length.

The monster is thought to have looked like a stockier version of the now-feared great white shark and weighed up to 100 tons.

Megalodon is recognizable by its huge vertebrae and teeth, which are triangular and have a diagonal length of almost eight inches.

It took famed fossil hunter Vito ‘Megalodon’ Bertucci nearly 20 years to reconstruct the jaw of a megalodon – the largest ever assembled – which measures 11 feet (3.5 meters) wide and nearly 7 feet (2 meters) high.

The Megalodon’s colossal mouth is said to have produced a raw force of 10.8 to 18.2 tons.

The ancient shark has been described as a super predator, as it could swim at high speeds and quickly kill a wide variety of prey, such as sea turtles and whales, in its strong jaws.