Barry hit the nail on the head ear-LYE on in this thread. Our language used to be a lot more elastic than it is now, and sailors were a thoroughly mixed lot, often speaking a pidgen landsmen wouldn't follow at all. Shanties were composed to fit a rhythm, and words would be twisted to fit the meter and rhyme. I also think Barry's right that you should sing what comes naturally to you, not to some model of "authenticity."