‘Many scientists don’t like to talk about shark sex,’ Juliet Eilperin writes in her entertaining study of sharks and their world. ‘They worry it will only reinforce the popular perception that these creatures are brutish and unrelenting.’ In as far as we understand the subject – only a few species have been observed mating – the business is ‘very rough’. Larger male sharks have to bite or trap the females to keep them around during courtship; marine biologists can tell when a female has been mating because her skin will be raw or bleeding. The process is so violent that, come the mating season, female nurse sharks will stay in shallow water with their reproductive openings pressed firmly to the sea floor. Otherwise they risk falling prey to roaming bands of males who ‘will take turns inserting their claspers in her’ (the clasper is the shark version of a penis, found in a pair behind the pelvic fins). A litter of fifty pups will have anything from two to seven fathers. But the reproductive story gets rougher still. A number of shark species go in for oophagy, or uterine cannibalism. Sand tiger foetuses ‘eat each other in utero, acting out the harshest form of sibling rivalry imaginable’. Only two babies emerge, one from each of the mother shark’s uteruses: the survivors have eaten everything else. ‘A female sand tiger gives birth to a baby that’s already a metre long and an experienced killer,’ explains Demian Chapman, an expert on the subject.

There are three defining events in modern American shark mythology. First, the attacks of 1916, when four people were killed in one week in five separate attacks off New Jersey, two at beach resorts and two in Matawan Creek, more than a dozen miles inland. It created mass hysteria, launched a wave of shark-hunts and gave rise to the myth of the serial man-eater – something that all the evidence tells us is wrong. The second was the sinking of the USS Indianapolis on 30 July 1945, in the final weeks of the Pacific War. The cruiser, which had delivered the uranium for the Hiroshima bomb, was sunk by a Japanese submarine between Guam and the Philippines. Of the 1200-strong crew, 300 were killed during the sinking; the survivors spent four days in the water, during which all but 317 were killed by exposure, dehydration and sharks. The third event was Jaws, which bundled up the earlier two into a slick package that spread rampant shark-phobia across the world: Peter Benchley’s novel was based on the Jersey attacks, and Quint, the Ahab-style shark hunter played with scenery-chewing vigour by Robert Shaw in the film, is a veteran of the Indianapolis disaster. Benchley, Eilperin says, did more to instil ‘intense fear and hatred of sharks than anyone else in the 20th century’. By bringing an age-old nightmare to life, he ‘gave it a credibility, a sense of concreteness, it had never had before’.