A lawsuit claims The Shape of Water ripped off the play Let Me Hear You Whisper. Here's a movie of it. There's a cleaning woman, a government lab, and a captive dolphin (who can "speak"). But the parallels end there as far as I'm concerned https://www.youtube.com/watch?v=SsUS0XudrQ0 …
Superficially. Beauty and the Beast and Creature from the Black Lagoon have better claims than this play. And I’m a theatre guy but a cleaning woman talking to a dolphin and a mite cleaning woman fucking a merman are very different. 