I can see what Jon means as he calls this “A crazy tune that takes some learning! We did a version of this song with Eliza And The Ratcatchers but this version is from Frankie Armstrong.”
Magic or simple cunning? Either way the maid in question does a nifty job of getting herself out of a tight spot. I’m guessing that the moonlight adds to the suggestion of a supernatural event and the sleeve notes for Martin Carthy’s version, as included on The Bird In The Bush also pick up on that as you’ll see on Mainly Norfolk. You’ll also find a YouTube video of Eliza & The Ratcatchers on the page. There are a number of threads circling around this on Mudcat, but I’ve not been able to pin down anything especially fascinating, although there is an extra verse about the maid suggesting she was somewhat lovelorn and hence prone to wander alone on the shore-o. You’ll see that both Eliza and Rachel McShane have included that if you compare and contrast the versions on the above link. It’s an interesting contrast to note the more recent versions start with this verse, which makes me wonder from whence it came. Someone more diligent than I might turn up a pearl on this. Please share it if you do.