Clarke's early nonfiction includes several titles specifically dealing with the sea and with diving. For several years in the 1950s and 1960s, Clarke was partner in a diving company with Mike Wilson. In the waters off Sri Lanka—then known as Ceylon—and elsewhere, they engaged in scuba diving, undersea photography, treasure hunting, and writing. With Mike Wilson, Clarke wrote Boy Beneath the Sea (1958), The First Five Fathoms: A Guide to Underwater Adventure (1960), Indian Ocean Adventure (1961), and Indian Ocean Treasure (1964). From that same range of experiences, Clarke was solo author of The Reefs ofTaprobane: Underwater Adventures Around Ceylon (1957), The Challenge of the Sea (1960) and, drawing on a trip to Australia's Great Barrier Reef, The Treasure of the Great Reef (1964). Thus, as Clarke writes of the conditions of the wreckage of the Titanic, or of the thrills and risks of diving and working underwater in...