Although the tone at the beginning of "The Swimmer" is light, it becomes contemplative, then ominous, and finally darkly surreal. These mood shifts occur subtly and match the waning energy Neddy feels as he progresses through the suburban swimming pools of the "Lucinda River." As Neddy's Sunday begins, he is in fine mettle, and although he is not a young man, descriptions of good health, youth, and fitness are used. He considers himself a "legendary figure," as well as "a pilgrim, an explorer, a man with a destiny." The first two pools that have people to greet him both proclaim his visit to be a "marvelous surprise."
By the time he makes it to the Levys' pool, however, he has had four or five drinks and is feeling tired, although he is still "pleased with everything." As he waits out a thunderstorm, the pacing of the narrative slows as well. Thunder, a train whistle, and rushing water display a more thoughtful rather than vibrant tone, and Neddy's memory begins to get foggy.
At Neddy's crossing Route 424, the story takes on a more ominous tone as drivers laugh and jeer at him and pelt him with garbage. His unpreparedness for his journey and his inability to turn back make the formerly pleasant day ugly, and that ugliness intensifies as he enters the public pool where the lifeguards rebuke him. Mrs. Halloran's cryptic sympathy for Neddy's "misfortunes" and the smell of smoke in the air create a sense of foreboding.
The story takes on a surreal tone when Neddy meets his old acquaintance who has no navel. Women who were formerly at his beck and call now spurn him. Strangely, it has become autumn during the course of a single day, and Neddy begins to cry for the first time in his adult life. Conquering the final pool with his last ounce of strength, he realizes his "triumph seemed vague" as he arrives home to a house that has been empty and shuttered for a long time.
As the story transitions from a realistic tale of suburbia to a surrealistic allegory, Cheever's tone subtly transitions as well.