Illustration by Arthur Hughes, in George MacDonald - The Light Princess, in Dealings With the Fairies, Alexander Strahan (London), 1867.
There seem to be a number of similarities between The Light Princess and the story of Undine, which George MacDonald admired, saying,
…of all fairytales I know, I think Undine the most beautiful.
George MacDonald - THE FANTASTIC IMAGINATION in A Dish of Orts : Chiefly Papers on the Imagination, and on Shakespeare, 1893.
Here is a snippet:
During the conversation, the stranger had already occasionally heard a splash against the little low window, as if some one were sprinkling water against it. Every time the noise occurred, the old man knit his brow with displeasure; but when at last a whole shower was dashed against the panes, and bubbled into the room through the decayed casement, he rose angrily, and called threateningly from the window: "Undine! will you for once leave off these childish tricks? and to-day, besides, there is a stranger knight with us in the cottage." All was silent without, only a suppressed laugh was audible, and the fisherman said as he returned: "You must pardon it in her, my honored guest, and perhaps many a naughty trick besides; but she means no harm by it. It is our foster-child, Undine, and she will not wean herself from this childishness, although she has already entered her eighteenth year. But, as I said, at heart she is thoroughly good."
Friedrich de la Motte Fouqué (tr. F. E. BUNNETT) - Undine, CHAPTER I, HOW THE KNIGHT CAME TO THE FISHERMAN.