His Bones are Coral is a 1955 thriller novel by the British writer Victor Canning. It was published in the United States with the alternative title of Twist of the Knife. The title is a reference to William Shakespeare's Full fathom five from The Tempest.
Howard Smith, a pilot flying between Cairo and Port Sudan with a cargo of illicit drugs crash-lands in the desert near a port on the Red Sea. Escaping from the wreckage and needing to find a way out of his problems, he accept an offer from a marine biologist to take part in a coral-finding expedition in shark-infested waters.
It was adapted into the 1969 American film Shark! directed by Samuel Fuller and starring Burt Reynolds, Arthur Kennedy and Silvia Pinal.