That's A Twenty Footer

The average length of a Great White shark is fifteen feet, which puts it at about two thirds the size of a school bus. Bigger specimens are not unknown. In 2009 fishermen off the coast of Queensland in Australia reeled in a ten foot shark that had almost been bitten in half by a bigger predator, which was estimated to be a twenty footer. This is the size Benchley settled on for his monster fish in the book. He helpfully provides some basic vital statistics - the head is four feet across, the dorsal fin is more than a foot high, and the tail even higher - but, rather than numbers, it is the reaction of the three characters that helps to convey something of the brutal majesty of the beast.

Quint remains unimpressed by the scale of the shark - "With them things, it don't make much difference over six feet. Once they get to six feet, they're trouble." - and dismisses the animal as "just a dumb garbage bucket." Hooper is in awe of the creature - "That fish is a beauty. It's the kind of thing that makes you believe in a god." - and reacts with the same enthusiasm he displayed when describing the species to Ellen in Chapter Six. Brody projects his own fears onto the fish - he reacts with a chill and a shudder (what his mother would have called the "wimwams"), and says, "You can't tell me that thing's a fish [...] It's more like one of those things they make movies about. You know, the monster from twenty million fathoms."

The film added five feet to the shark's length and tweaked the intial reactions of the three main characters. Hooper exudes boyish enthusiasm and can barely contain his excitement as he snaps pictures for a future issue of National Geographic. Brody is at first paralysed with shock and momentarily incapable of action ("How do we handle this?"). Only Quint remains unmoved, assembling his harpoon gun, dismissing the interruption of a radio call from the Amity coastguard, and issuing orders in a calm but commanding tone.