The Cruel Sea is divided into seven parts, one for each year from 1939 through 1945, and the narrative is in chronological order. The effect is of a chronicle, as the third-person narrator follows two ships and their crews.

First, HMS Compass Rose is followed, from her fitting out until her sinking in the North Atlantic, the victim of a submarine. Second, most of the handful of Compass Rose survivors and the narrative are transferred to HMS Saltash.

Although Lieutenant Lockhart is the main character, the focus often shifts to various others. As Monsarrat himself puts it in his introduction, the book is "the story of one ocean, two ships, [and] about a hundred and fifty men."

Monsarrat's style is gracefully transparent, with much use of dialogue, and frequent omniscient insights into characters' feelings and thoughts. The many little details — technicalities of naval procedures and equipment, the frequent encounters...