" Stop it,” came Eustace’s voice, squeaky with fright and bad temper. “It’s some silly trick you two are playing. Stop it. I’ll tell Alberta--Ow!”
The other two were much more accustomed to adventures, but, just exactly as Eustace Clarence said “Ow,” they both said “Ow” too. The reason was that a great cold, salt splash had broken right out of the frame and they were breathless from the smack of it, besides being wet through.
“I’ll smash the rotten thing,” cried Eustace; and then several things happened at the same time. Eustace rushed toward the picture. Edmund, who knew something about magic, sprang after him, warning him to look out and not to be a fool. Lucy grabbed at him from the other side and was dragged forward. And by this time either they had grown much smaller or the picture had grown bigger. Eustace jumped to try to pull it off the wall and found himself standing on the frame; in front of him was not glass but real sea, and wind and waves rushing up to the frame as they might to a rock. He lost his head and clutched at the other two who had jumped up beside him. There was a second of struggling and shouting, and just as they thought they had got their balance a great blue roller surged up round them, swept them off their feet, and drew them down into the sea. Eustace’s despairing cry suddenly ended as the water got into his mouth.
Lucy thanked her stars that she had worked hard at her swimming last summer term. It is true that she would have got on much better if she had used a slower stroke, and also that the water felt a great deal colder than it had looked while it was only a picture. Still, she kept her head and kicked her shoes off, as everyone ought to do who falls into deep water in their clothes. She even kept her mouth shut and her eyes open. They were still quite near the ship; she saw its green side towering high above them, and people looking at her from the deck. Then, as one might have expected, Eustace clutched at her in a panic and down they both went. "
― C.S. Lewis , The Voyage of the Dawn Treader (Chronicles of Narnia, #3)