I also heard this on the New Golden Ring and have known it from years back (can't remember from where, but probably from an older Golden Ring album.

Instead of singing "on board a man o' war," it is sung "on board the ('de')man o'war. The "Hey" after each first line, is really emphasized (by everyone, when singing with a host of folks). Can be sung in unison or harmony (has great harmonies). In addition to Captain, Golden Ring sings "cook,"gunner," "mate" and "steward."

Jim