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."
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.
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!"