Frank Herbert's first novel. It was also published with the title "Under Pressure".
It tells the story of a war in the future where advanced submarines prowl the seas. The great pressure placed upon these crews combined with a growing mission failure rate prompts the insertion of an undercover psychologist onto a submarine to study the crew behavior and to capture a spy.
Herbert was apparently questioned by the U.S. military for this novel, who threatened to have it pulled. At the time it came out the U.S. submarine fleet was advancing into new doctrine and operating procedures. It was felt that Herbert's writing was too close to the truth not to be the work of a spy. This is similar to the experience of Tom Clancy for his book The Hunt for Red October, however Herbert's was a 100% creative and visionary work of science fiction rather than constructed from interviews with sailors and study of technical documents of the boats in question.