Novellas about merfolk

Roverandom is a novella by J. R. R. Tolkien, originally told in 1925, about the adventures of a young dog, Rover. In the story, an irritable wizard turns Rover into a toy, and Rover goes to the Moon and under the sea in order to find the wizard again to turn him back into a normal-sized dog. The author wrote Roverandom for his son Michael to amuse him upon the loss of his favourite toy, a little leaden dog which he lost on a beach of grey shingle stones the same size and colour as the toy. The work is in tone a children's story, but contains many allusions and references in the manner of Farme

1961 short story by Giuseppe Tomasi di Lampedusa