When I learned this song ca1964 (from one book or another), the word was "bows."

I suspect that "nose" may have come from a landubber's mishearing. Most people don't know that "bows" is as acceptable a description as "bow."

And there is a "Southern star": Polaris Australis (Sigma Octantis) visible only in the Southern Hemisphere. Unfortunately it's usually too dim to be useful to navigators.

However, it does indicate in the song that the ship is headed south of the equator.