I believe there was a YA book of ironic stories that I read between 1979-1983, though it may have been published earlier.
Story I’m looking for: A teenage boy discovers a mermaid living in a pond at the bottom of a quarry. She never breaks the surface of the water, but looks beautiful underneath it. The quarry will soon be dynamited and caved in, so he decides to save her and move her to another pond. When he does capture her, with much difficulty, she is a hideous monster (the water had distorted her features) that nearly kills him. He lets her stay in the pond. The next day the quarry is dynamited and she is buried under the rubble.
The story could have been written earlier than the 1970s, but was probably no earlier than the 60s. I originally thought it was in the same anthology as another ironic story I finally found the name for (“Blue Eyes” by Maurice Level), but every anthology that story was in doesn’t seem to have the mermaid story.