The creature he's referring to is megalodon, an extinct species of shark which - because its fossilised teeth were similar (not "exactly like" as Hooper claims) to those of the Great White - was assigned to the genus Carcharadon. In fact, little of the megalodon has survived in the fossil records except for its teeth and fragments of vertebrae - its shark cartilage skeleton would have been eroded rather than preserved by time. It is from this limited amount of evidence that scientists have attempted to reconstruct the creature, using the Great White (Carcharodon carcharias) as a template. The tooth of a Great White averages about three inches in length and weighs a couple of ounces whilst the largest megalodon tooth measures more than twice that size at seven inches and weighs in at more than a pound. Early estimates of the creature's size - based around a 1909 jaw reconstruction - put it at ninety eight feet, and this presumably is the statistic that Peter Benchley came across in his research for the novel. Coincidentally, it was in 1973 - the year he delivered his manuscript - that scientists came up with a revised figure of forty to fifty feet. Despite a lot of scientific squabbling since then on how to arrive at an accurate estimate, the consensus among experts today seems to be that the megalodon had a total length of fifty two feet.
Hooper expounds on the theory that the megalodon may still lurk in the deepest depths of the oceans:
"What's to say megalodon is really extinct? Why should it be? Not lack of food. If there's enough down there to support whales, there's enough to support sharks that big. [...] They'd have no reason to come to the surface. All their food would be way down in the deep. A dead one wouldn't float to shore, because they don't have flotation bladders. Can you imagine what a hundred-foot white would look like? Can you imagine what it could do, what kind of power it would have?"
This is not a view that is shared by the experts. It is generally believed that the megalodon became extinct about one and a half million years ago as a result of changes in global ocean circulation and a subsequent reduction in the creature's food supply. It's quite likely that it even "had to resort to cannabilism to stay alive."
The megalodon does still exist in the popular imagination. Science fiction author Steve Alten has made a successful writing career out of a series of novels involving a megalodon, and direct-to-video movie studio the Asylum had a surprise hit on its hands in 2009 when the trailer for Mega Shark versus Giant Octopus went viral.
