During World War II, Ernest Hemingway and his beloved boat Pilar embarked on a mission to destroy German submarines that they encountered along the Cuban coast. The mission is recounted in Terry Mort's new book, The Hemingway Patrols: Ernest Hemingway and His Hunt for U-Boats.
Ernest Hemingway never spotted a German submarine, but that may have been the goal all along. According to Mort, the true appeal of the mission was: "the quest, the adventure, the serious purpose, the voluntary service, the fun, the satisfaction of command and comradeship, the joy of being at sea, the craft of seamanship and navigation, the possibility of danger, and the piquancy of not knowing whether it will come, the reality and the metaphor of an unseen enemy suddenly rising."
If you want to read Hemingway's own fictional account of chasing German sailors of a sunken U-boat, see part III ("At Sea") of his 1970 book, Islands in the Stream.