A perfect day for bananafish

«They waded out till the water was up to Sybil’s waist. Then the young man picked her up and laid her down on her stomach on the float.
“Don’t let go,” Sybil ordered. “You hold me now.”
“Miss Carpenter. Please. I know my business,” the young man said. “You just keep your eyes open for any bananafish. This is a perfect day for bananafish.”
“I don’t see any,” Sybil said.
“That’s understandable. Their habits are very peculiar.” He kept pushing the float. The water was not quite up to his chest. “They lead a very tragic life,” he said. You know what they do Sybil?”
She shook her head.
“Well, they swim into a hole where there’s a lot of bananas. They’re very ordinary looking fish when they swim in. But once they get in, they behave like pigs. Why, I’ve known some bananafish to swim into a banana hole and eat as many as seventy-eight bananas”. He edged the float and its passenger a foot closer to the horizon. “Naturally, after that they’re so fat they can’t get out of the hole again. Can’t fit through the door.”
“Not too far out,” Sybil said. “What happens to them?”
“The bananafish.”
“Oh, you mean after they eat so many bananas they can’t get out of the banana hole?”
“Yes,” said Sybil.
“Well, I hate to tell you, Sybil. They die.”
“Why?” asked Sybil.
“Well, they get banana fever. It’s a terrible disease.”»

J. D. Salinger, A Perfect Day for Bananafish