This episode page has been compiled from the episode description at the NDR website.
Finchen looks after Ella's seashell. She has had it for a long time, but has been unable to open it; the story says that it contains a treasure. Finchen drops it in a vase filled with water that cause the shell to open up. Muriel, a water nymph appears. She sings a song to Finchen about being underwater and hands Finchen a perl and the disappears back into the shell.