Dr Blanke has just been called up to serve as ship's doctor on the Boon. He knows nothing of the Navy so he is grateful for some wise advice from a warrant bo'sun when he signs on. He is to be taken to join the Boon by a chartered Dutch ship, the Wilhelmina, which is also carrying a number of American soldiers. The Wilhelmina is torpedoed and Blanke finds himself in a life raft with a lot of soldiers and two Javanese members of the crew who speak hardly any English. Since Blanke is the only Naval officer on board the troops naturally look to him to assume command. He has no choice but to take on this role and try to work things out from first principles. With the help of the Javanese, who know about starting the motor and setting the sails, Blanke keeps everyone alive until they are spotted from the air and rescued.
"Counterpunch" describes how the Boon intercepts a much more heavily armed Japanese cruiser, thanks to the newly installed radar (a British invention, of course). Captain Angell takes the Boon close to the enemy ship during the night and sinks it with torpedoes.
The book needs to be seen in the light of the political situation at the time. During the second world war Forster was in the United States, where he worked for the British Information Service and wrote propaganda to encourage the US to join the Allies. The stories in this book were written after this had happened, following Pearl Harbor. I get the impression that they were intended to encourage the Americans to feel that they were engaged in an important cause, and were going to win. There is a considerable element of heroism, or at least great devotion to duty, in all the stories, one of which concerns a Cockney Britisher in alliance with a giant American friend (a significant combination).