n The Dragon in the Sea (also published as Under Pressure and 21st Century Sub) the plot focuses on Ensign Ramsey, a psychologist assigned to monitor the crew of a submarine that is on a dangerous mission. Nervous breakdowns among crew members have been attributed to acute paranoia induced by the dangers of underwater warfare and a possibly insane captain.

By making a psychologist the novel's main character, Herbert is able to explore in detail the effects on people of prolonged periods of isolation from normal society. The immense weight of the water of the oceans becomes a metaphor for the pressures on the submariners. The novel's suspense grows intense as Ramsey recognizes psychological problems in himself as well as in his shipmates. He cannot be sure if his observations are accurate or skewed by his own paranoia that there might, indeed, be a saboteur.