"Dip in the Pool" is a macabre short story by Roald Dahl that was originally published in the 19 January 1952 edition of The New Yorker. It later appeared in the 1953 collection Someone Like You.
On a cruise ship, there is a betting pool each day where guests try to correctly guess the amount of miles that the ship will travel each day, within ten miles above or below the captain's own guess. Guests can also choose "low field" or "high field," those being any amount more than ten above or ten below. On one particularly stormy day, a guest named Mr William Botibol bids two hundred pounds on "low field", hoping that the storms will significantly slow down the ship. He is gambling largely with money he doesn't have (it represents years of his and his wife's savings), but he views it as worth the risk.
The next morning, he woke up to find that the sky is clear and the ship is moving very fast to make up for lost time. Distraught, he decides that to slow down the ship, he will jump off into the water - this way, they will have to stop and turn around to rescue him. The count of miles for each day ends at noon.
Seeking out potential eyewitnesses, Botibol ventures to the rear of the ship where he encounters a single, rather large middle-aged woman. Striking up casual conversation with her, talking about the gambling and other things (in order to ensure that she notices him and is really willing to help, and therefore, when he falls into the water), he then surreptitiously leaps off the end of the ship. Yelling "Help, Help!" as he plunges into the water beneath him, he captures the attention of the woman. Initially she seems unsure about how to react, but eventually relaxes and watches as the bobbing head of Botibol, arms waving madly and shouting something she does not hear, disappears into the distance.
A thin, commanding, matronly woman arrives on the same deck, and reprimands the larger woman. The bony woman states that she has been looking for the larger woman for quite a while, and scolds her for wandering off. The larger woman doesn't reply directly, but instead remarks offhandedly about a man that "dived overboard...with all his clothes on", a comment that earns a stern "Nonsense!" from the motherly lady. The last scene is that of the young woman "allowing herself to be led away across the deck" and offhandedly mentioning "Such a nice man. He waved to me"; the reader is left with the impression that the larger woman may be mentally handicapped or have some mental condition such as autism.