How does Ernest Hemingway use imagery in Islands in the Stream?

In Part III, Chapter III, an allegorical image arises in the joking between the lieutenant and Thomas about a pig that swims out to sea in terror and drowns. This could symbolize the Germans attempting to escape and the suicidal nature of a world at war. When Hemingway uses symbolism and allegory, he applies the techniques lightly and with faultless placement in the story. Here the image of the pig out of its element gains prominence through the joking between Thomas and the lieutenant.