"The Submarine," an enormous and mythical great white shark that supposedly terrorized South Africans 30 to 44 years ago, might have actually existed, suggest experts who offer logical explanations for some of the extraordinary witness accounts.

Said to be anywhere from 22 to 30 feet long, The Submarine was reported to be in False Bay, South Africa, according to marine biologist Alison Towner of the nearby Dyer Island Conservation Trust. The region is still famous for its large great whites and other sharks.

"During the 1970s to the early 1990s, various anglers fished from small vessels and reported sightings of huge white sharks in False Bay," Towner told Discovery News, adding that some of these individuals later turned to trophy fishing for the sharks before great whites gained protected status in South Africa in 1991.

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A few of The Submarine seekers penned popular books, such as Theo Ferreira's "Shark Man: My Obsession with the Great White," which helped to further fuel the legend.

"We caution the reliability of the actual size of this Submarine (shark) as it is actually very difficult to estimate the size of a great white when it is in the water, especially when fighting it on rod and reel as was the case in many accounts of The Submarine," Towner said.

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"Further," she continued, "if one is standing on a boat, particularly a smaller boat almost on level with the water, the shark can appear to be much bigger than, for example, (if the person is) standing on a larger elevated vessel."

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She and Neil Hammerschlag, a shark expert who has studied great whites in South African waters, told Discovery News that the maximum length great whites can attain is around 20 feet long from snout to upper caudal lobe (tail) tip.

Hammerschlag, a research assistant professor in the Department of Marine Ecosystems and Society at the University of Miami, added that there is no truth to reports of great whites reaching 30 feet in length or more.

John McCosker, chair of Aquatic Biology at the California Academy of Sciences, said that a shark caught in waters off of Cojimar, Cuba, in 1945 supposedly was 21'3" long. It was never accurately weighed or measured, although McCosker saw a tooth removed from this shark’s jaw, and he said it could have come from a 21 footer, as described.

A large great white shark.sharkdiver.com, Wikimedia Commons

Yet another great white, found near Kangaroo Island in South Australia, purportedly was around 22 feet long, but only its head and pectoral fin were saved. McCosker said he has seen white sharks "that are at least 18 feet long off Dangerous Reef, South Africa."

He doubts that a great white could grow much larger than those sizes, or weigh more than 3 to 4 tons.

"The problem becomes one of maneuverability," he explained. "A shark that large has great difficulty capturing live prey and would have to survive by eating large mammal carcasses."

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The largest sharks, such as basking sharks and whale sharks, tend to be more gentle and passive filter feeders. Whale sharks can grow up to around 41.5 feet long.

"When sharks become as large as that, they can only survive by filter feeding, like the great whales, which are the largest mammals on earth," McCosker said.

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Filter feeding targets tiny creatures, such as zooplankton, which are plentiful, low on the food chain and require minimal effort to obtain.

The Submarine was therefore probably a very large great white, but not as big as it was rumored to be.

Towner also reminds that white sharks are slow growing, so big individuals tend to be exceptionally old. The exciting Submarine accounts of legend lose some of their thunder when one considers that the fishermen likely would have been fighting elderly sharks close to kicking the proverbial bucket.

She also warns, "If we jump to the conclusion that there's plenty of huge ones (great whites) out there, it may be a misleading and damaging representation of the real situation. Remember, 100,000,000 sharks are killed annually by humans!"