Ordinary- Naut. laid up, out of condition (OED). I think you are correct in using the nautical meaning.
I couldn't find any help on the 'mermaid condition," except that mermaid was an old sailors term for a prostitute, not what is wanted here. I think that is means that the gel wound herself up to 'sing' long and loud, like sirens do. Agreeing with Liz the Squeak.