Sexual appetites and activity at times appear in explicit detail in Cradle, a factor that collaborator Gentry Lee admits to Clarke's biographer Neil McAleer were "overdone" in comparison to Clarke's usual discretion in addressing human sexuality. The malefemale conflicts of the novel are those raised for discussion in the news media and pop psychology books in the 1980s. Those very tensions, however, are not merely superficial commentary.

If Carol Dawson and Nick Williams were not able to cooperate and overcome their hostilities to some degree, they would not have been able to solve the central problem of the novel — discovering the aliens' need and meeting it well enough to protect the future of humanity.

Clarke's familiarity with diving and the undersea environment shows in the realistic details of the setting, the characters' attention to safety precautions when diving, and so forth. Clarke's young adult nonfiction...