Palaeontologists working along the shores of Chesapeake Bay have been searching for evidence of the largest shark ever to inhabit the oceans, a species known as the megalodon. Their work focuses on fossil remains that may help explain the biology and eventual extinction of this prehistoric predator.
One of the most famous accounts associated with the megalodon dates back to 1918, near Broughton Island off the coast of New South Wales, Australia. A crew of experienced spiny lobster fishermen working out of Port Stephens reported a confrontation with an enormous marine animal. These fishermen were familiar with local waters, including the dangerous currents and unpredictable weather around Broughton Island, and were accustomed to heavy physical labour.
On that morning, the crew was pulling large wooden lobster traps from deep water. These were sturdy structures, roughly three feet in diameter, weighted to rest on the sea floor and attached to thick hemp ropes. The work was demanding and required the full strength of the crew and the boat’s winch.
As the crew began hauling one of their heaviest lines, the tension suddenly increased, nearly causing the vessel to lose its balance. The water around the boat became disturbed, and a large shadow rose from below. According to the fishermen, a creature of immense size broke the surface beside their boat. They described a pale-coloured head, reported to be as wide as a pier shed, which took the heavy wooden traps in a single bite, cutting the thick ropes and pulling the equipment, including its iron weights, beneath the surface.
The crew did not attempt to recover their gear. They returned to Nelson Bay and refused to go back out to sea. These were men whose livelihood depended on daily fishing in difficult conditions, yet they left their equipment behind and reported the incident to local authorities.
The story reached the New South Wales Department of Fisheries, and a senior official, naturalist David George Stead, investigated the case with an inspector named Payton. Stead was a respected scientist and author of marine life studies. He interviewed the crew members individually. Their accounts were consistent. The men described a shark-like creature of pale colour with an extraordinarily wide head. Their estimates of its total length ranged from roughly 115 feet to as much as 300 feet. Stead noted that human perception under extreme stress is often unreliable, but he also acknowledged the physical evidence: expensive commercial traps had disappeared, and thick hemp lines had been broken by a sudden, powerful force rather than by wear or rot.
Stead later published the account in his 1963 book, “Sharks and Rays of Australian Seas.” In his writing, he struggled with the data. As a scientist, he recognised that a shark of that size exceeded modern biological limits. As an investigator, he accepted that the fishermen had encountered a large and violent marine predator that science had not documented. The incident was never resolved.
To understand what might have caused such a sighting, researchers look to the megalodon, which lived from roughly 23 million years ago until about 3.6 million years ago. The megalodon belonged to a separate lineage of sharks known as Otodontidae, distinct from the modern great white shark. Fossil evidence, primarily teeth measuring more than seven inches along the diagonal edge, suggests that adult megalodons reached lengths of 50 to 60 feet and weighed between 50 and 70 metric tons. That body mass was roughly 30 times greater than the largest recorded great white shark.
The megalodon had a mouth estimated at up to ten feet wide, lined with five rows of thick, serrated teeth designed for breaking bone. Computer modelling has estimated its bite force at more than 18 tons per square inch, substantially greater than the bite force of a great white shark. Its skeleton was made of dense, flexible cartilage rather than bone, which allowed for agility despite its size. Evidence also suggests the megalodon could regulate parts of its body temperature, enabling it to hunt in both warm tropical waters and cooler temperate regions.
Fossilised whale remains show bite marks on rib cages, shoulder blades, and spines, indicating that the megalodon attacked its prey directly through thick bone. It likely targeted balleen whales, ancient sperm whales, giant sea turtles, sirenians, and large pinnipeds. Researchers believe it would strike small or medium whales from below, and against larger whales it would first bite the flippers and tails to disable them, then deliver a fatal bite to the chest cavity. The megalodon used shallow coastal bays as nursing grounds, giving birth to live young that measured six to ten feet at birth.
The megalodon disappeared from the fossil record during the late Pliocene, around 3.6 million years ago. The cause appears to have been a combination of planetary changes rather than a single catastrophic event. The formation of the Isthmus of Panama closed the Central American Seaway, disrupting warm water circulation between the Atlantic and Pacific Oceans. Global temperatures dropped, ice caps expanded, and shallow warm waters that served as birthing grounds became cold or disappeared. Balleen whales adapted by developing thick blubber and migrating toward the colder, food-rich waters of the polar regions. The megalodon’s energy requirements were too high for those frozen waters.
At the same time, new competitors emerged. Early ancestors of the great white shark spread across oceans and competed for the smaller marine mammals that young megalodons relied on. Coordinated, intelligent predators, including early orcas and predatory sperm whales, hunted in organised groups and outcompeted the solitary megalodon for available food. The megalodon’s enormous size, once its greatest advantage, became a fatal weakness when resources became scarce. It could not follow its prey to colder waters, was excluded from its coastal nurseries, and was outhunted by faster competitors. The species slowly went extinct.
The deep sea remains largely unexplored. More than 80 percent of the world’s oceans have not been mapped or observed directly. This has led to speculation about whether a massive predator could survive in the deep trenches. In deep-sea environments, some species reach sizes far larger than their shallow-water relatives, a phenomenon known as abyssal gigantism. Giant isopods and colossal squid, which can exceed 40 feet, are examples. Some acoustic recordings have captured low-frequency sounds from deep water that have not been definitively attributed to any known species, though famous examples such as the “Bloop” were later identified as ice quakes in Antarctica.
Biologically, it would be difficult for a predator of the megalodon’s size and metabolism to survive in the deep ocean on a permanent basis. The megalodon was adapted to hunt air-breathing marine mammals near the surface and along the coast, not to live in cold, high-pressure, low-food environments. However, some modern deep-sea sharks, such as the Greenland shark, do grow to enormous sizes and live for centuries in cold, low-light water with a very slow metabolism. Whether any ancient shark lineage could have adapted in a similar way remains unknown.
Sightings of unusually large marine animals have continued across the Pacific over the decades. During World War II, sonar operators and surface lookouts on warships reported large submerged targets and dark dorsal fins. In the 1960s, a merchant captain near the Tuamotu Archipelago reported seeing a pale, very large shark beside his 55-foot vessel, with a head he estimated at 12 feet wide. There is no confirmation of these stories, and eyewitness accounts are subject to error, exaggeration, and fear. A large or oddly coloured great white shark or a slow-moving whale shark could conceivably be misinterpreted as something far larger. Yet the detail that a creature reportedly pulled thousands of pounds of weighted commercial equipment and severed thick hemp ropes remains unexplained by known biology.
The 1918 Port Stephens incident has grown into a persistent part of maritime folklore. The story has been revisited in documentaries and fiction, including films and cable television specials about the possibility of a surviving prehistoric shark. Those productions are speculative. The historical account, however, is limited to what Stead documented about the fishermen’s testimony and the lost equipment.
The fishermen themselves gained no fame and no money from telling their story. They simply lost their tools and their income and refused to return to the water. Their decision to accept financial ruin rather than go back to sea is the most disturbing fact of the incident. Whatever they saw that morning, their fear was genuine. The ocean remains a place where human knowledge is incomplete, despite modern technology. Whether the fishermen encountered a genetic anomaly, a surviving prehistoric animal, or something that science cannot yet classify, the incident remains unresolved.
