The Famous Five adventure series features a few swimming scenes, as the super-slueths take off in their school hols fighting crime and evil-doing the length and breadth of England - well the West Country part of it, really.
Here's bossy Julian, wimpy Ann, tomboy George and gormless Dick (not to forget Timmy the Dog) and all the Blyton sexist and class-based stereotypes played out in some swimming secnes.
Extract from Five Get Into Trouble (first pub Nov 1949):
"Now for the lake," said Julian, folding up the map which he had just been examining. "It's only about five miles away. It's called the Green Pool, but looks a good bit bigger than a pool. Gosh, I could do with a bathe. I'm so hot and sticky."
They came to the lake at about half-past seven. It was in a lovely place, and had beside it a small hut which was obviously used in summer-time for bathers to change into bathing suits. Now it was locked, and curtains were drawn across the windows.
"I suppose we can go in for a dip if we like?" said Dick, rather doubtfully. "We shan't be trespassing or anything, shall we?"
"No. It doesn't say anything about being private," said Julian. "The water won't be very warm, you know, because it's only mid-April! But after all, we're used to cold baths every morning, and I daresay the sun has taken the chill off the lake. Come on - let's get into bathing-things."
They changed behind the bushes and then ran down to the lake. The water was certainly very cold indeed. Anne skipped in and out, and wouldn't do any more than that.
George joined the boys in a swim, and they all came out glowing and laughing. "Gosh, that was cold!" said Dick. "Come on - let's have a sharp run. Look at Anne dressed already. Timmy, where are you? You don't mind the cold water, so you?"
The next day was fair and bright. It was lovely to wake up and feel the warm sun on their cheeks, and hear a thrush singing his heart out....
"I'm going for a bathe," said Julian. "Anyone else coming?"
"I won't," said Anne. "It will be too cold for me this morning. George doesn't seem to want to either. You two boys go by yourselves. I'll have breakfast ready for when you come back. Sorry I won't be able to have anything hot for you to drink - but we didn;t bring a kettle or anything like that."
Julian and Dick went off to the Green Pool, still looking sleepy. The two boys were almost at the pool. Ah, now they could see it between the trees, shining a bright emerald green. It looked very inviting indeed.
They suddenly saw a bicycle standing beside a tree. They looked at it in astonishment. It wasn't one of theirs. It must belong to someone else.
Then they heard splashings from the pool, and they hurried down to it. Was someone else bathing?
A boy was in the pool, his golden head shining wet and smooth in the morning sun. He was swimmign powerfully across the pool, leaving long ripples behind him as he went. He suddenly saw Dick and Julian and swam over to them.
"Hallo," he said, wading out of the water. "You come for a swim too? Nice pool of mine, isn't it?"
"What do you mean? It isn't really your pool, is it?" said Julian.
"Well - it belongs to my father, Thurlow Kent," said the boy.
Both Julian and Dick had heard of Thurlow Kent, one of the richest men in the country. Julian looked doubtfully at the boy.
"If it is a private pool we won't use it," he said.
"Oh, come on!" cried the boy, and splashed cold water all over them. "Race you to the other side!"
And of all three of them went, cleaving the green waters with their strong brown arms - what a fine beginning to a sunny day!
The marvellous website Enid Blyton.net provides a plot summary of each of the books, and some reproductions of illustrations.
In Five Go To Billycock Hill, "Toby takes the Five down to a pool for a swim, but Julian is concerned about the sign that informs them the area is restricted. Toby tells them it's been there ages and doesn't mean anything, so they all plunge in—but soon an officer arrives from the RAF base and tells them to clear off. So swimming is out. But Julian sets things right by apologizing in a most grown up way that impresses the officer no end. Good old thirteen-year-old Ju! "
In Five Have Plenty of Time, "The Five are once more staying at Kirrin Cottage and enjoying the sunshine and swimming in the bay."