My source for it is Fifty Sailors' Songs or Chanties - Boosey circa 1870. And it does in fact say it is a chanty. I agree with you that it doesn't have much the feel of a shanty to me. But then several songs that are shanties don't - at least not in the incarnations I'm familiar with - songs like Spanish Ladies or The Stormy Winds Do Blow (the other Mermaid song).

I believe I've read a few times at DT that many shanties lost their shanty character when they came to land (or when the days of working to shanties passed). I'd bet Digital Shantymen like Barry could come up with a huge list - heck they might have already done so in another thread!