You should be able to replay the mermaid's song, as long as she isn't in the middle of singing or while you are submitting an answer. I'll look into that for you!
Ah, yeah, it might've been because I failed, and the shells were still there from my last attempt when I tried to listen to the song again. A small blurb about that in the instructions would help, since it's not the most intuitive thing. But overall, it's a pretty small thing.
