Nick, As I'm sure you well know, Tom Lewis, former RN submariner, wrote the last shanty. I would consider it a shanty.

But what the point everyone is trying to make is that the traditional meaning for a shanty is a work song used to keep the pace of a job on ship.

But as times change, so do definitons. Nowadays, I believe for the average person, shantys basically are any song in a folk style dealing with the sea.