The largest ocean predator ever was likely the prehistoric shark Megalodon (Otodus megalodon), a giant shark that dominated ancient seas, reaching lengths of up to 20 meters (60+ ft) and weighing over 90 tonnes, preying on whales with its massive jaws. Other contenders for sheer size include giant marine reptiles like Ichthyotitan (a huge ichthyosaur) and massive predatory whales like Livyatan melvillei, but Megalodon is generally considered the biggest fish predator.
For nearly 20 million years the enormous shark dominated the oceans until becoming extinct just 3.6 million years ago. O. megalodon was not only the biggest shark in the world, but one of the largest fish ever to exist.
Not sure how you are measuring “greatest predator” of all time, but Megalodon was neither the largest nor longest lasting. If going by largest, then Blue Whale still wins. It's easy to forget they are apex predators.
In fact, Megalodon might not even have been the largest predator in the ocean at the time it was alive - the recently discovered Leviathan whale (Livyatan melvillei) was potentially larger than Megalodon and occupied the same territorial waters.
The Livyatan whale: A top Apex predator that hunted the Megalodon.
Of all the ocean predators, the great white shark seems like it might be best able to take on an orca. These huge sharks can measure up to 6.4m long and weigh as much as 2,041kg (that's heavier than a Ford Focus).
Key Takeaways. Leviathan, known properly as Livyatan, was a massive whale weighing as much as 50 tons. Leviathan had longer teeth than any other animal, even bigger than its rival, the shark Megalodon. Leviathan's extinction was likely due to the loss of its main food sources like seals and dolphins.
No, 25-foot great white sharks likely don't exist; while historical reports claimed massive sizes (up to 37 ft), current scientific consensus confirms the largest reliably measured great whites are around 20 feet (6 meters), with most adults being smaller, though females are generally larger than males, with the fictional "Jaws" shark being significantly larger than any verified real shark.
The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9–30.5 m (98–100 ft) and weighing up to 190–200 t (190–200 long tons; 210–220 short tons), it is the largest animal known to have ever existed.
At a length of more than 50 feet (15 metres) and a mass of nearly 50 tons (tonnes), Megalodon was both larger and heavier than Tyrannosaurus rex.
The Great White Shark is considered the deadliest shark due to having the most recorded unprovoked attacks and fatalities, followed closely by the Tiger Shark and Bull Shark, which are also responsible for numerous attacks in coastal areas. Great Whites are apex predators known for their powerful bites and curiosity, often mistaking humans for prey like seals.
Why did the Mosasaurus go extinct? The group died out during the course of the mass extinction event triggered by the extraterrestrial impact that formed the Chicxulub crater about 66 million years ago.
The biggest great white sharks can reach up to 20 feet long, but most are smaller. The average female is 15-16 feet long, while males reach 11-13 feet.
Great white sharks, to be exact. But the true ruler of the sea is the killer whale. Killer whales are apex predators, which means they have no natural predators. They hunt in packs, much like wolves, which are also at the top of their food chain.
The last megalodon likely died due to a combination of factors around 3.6 to 2.6 million years ago, primarily climate change, leading to a loss of its primary food source (baleen whales) and increased competition from emerging predators like great white sharks and orcas, forcing it out of its preferred warm waters. The cooling climate caused prey to shift to colder poles, while sea level drops reduced vital nursery areas, making survival unsustainable for the giant shark.
So, while great whites are dominant predators, they're outmatched by the orca. There's even footage of an orca hunting and killing a great white — off the coast of South Africa's Mossel Bay. Orcas target sharks for their nutrient-dense livers, which comprise up to a third of their body weight.
Titanosaurs such as Puertasaurus, Patagotitan and Argentinosaurus were the longest and heaviest of them all - far longer than a blue whale and perhaps as heavy as 10 or more elephants.
Collisions with ships, or ship strikes, are one of the biggest threats facing blue whales today. This happens when shipping lanes are constructed in areas where whales are found. Due to their huge size and low agility, blue whales are very vulnerable to ship strikes.
List of Strongest Animal in the Ocean
An adult great white shark has just one predator: the orca. Until recently, orcas have only been observed regularly preying on these sharks in South Africa, where they usually prefer to hunt larger adults, which provide more food once caught.
If a shark charges, fight back
“That happens nine times out of 10.” If that does not work, and a shark tries to bite a swimmer—or even has a limb in its mouth—Naylor says the best course of action is to poke the shark hard in the eyes.
Although Deep Blue was tagged with a short-term tracking device in 2014 by the Woods Hole Oceanographic Institution, the tracker became dislodged. Scientists can only speculate about where and when she will turn up next. As of 2024, Deep Blue was still alive, but there have been no confirmed sightings in 2025.
The fact that the whale has survived and apparently matured indicates that it is probably healthy. Still, it is the only one of its kind detected anywhere, and there is only one such source per season. Because of this, the animal has been called the loneliest whale in the world” (source).
“God created the great sea monsters and every living creature that moves, of every kind, with which the waters swarm” (Gen. 1:21). There is no greater creature on earth—land or sea—than the blue whale.
It probably didn't hunt megalodon or rather Livyatan most likely only went after juvenile Megalodon while Megalodon most likely only went after juvenile Livyatan . Most apex predators don't go after each other for sustenance and I could only see a megalodon and Livyatan come to blows over food.