"Dip in the Pool" is a macabre short story by British writer Roald Dahl, originally published in the 19 January 1952 edition of The New Yorker.
On a stormy day, a passenger named William Botibol bids £200 on "low field", the inclement weather having significantly slowed down the ship.
After striking up a casual conversation to ensure that she notices him and will raise the alarm when he falls into the water, he then surreptitiously leaps off the end of the ship.
Initially, she seems unsure how to react, but she eventually relaxes and watches as Botibol, arms waving madly and shouting, disappears into the distance.
The older woman does not reply directly but instead comments offhandedly about a man who "dived overboard... with all his clothes on" – a remark that earns a stern "Nonsense!"