Shakespeare it isn't -- doggerel, but with rhythm and rhyme enough to keep in your mind. "As you draw near to the Fogo land, you'll have fifteen fathoms in the sounding sand, -- From fifteen to eighteen, never more, and that you'll have close to the shore."
At the moment the linked site only has the one sample.
The site also has a collection of shanties and of sea songs. I assume these are slightly sanitized versions. Hard work, alcohol and female company are prominent. "The other mornin' I was walkin' by the river When I saw a young girl walkin' With her topsails all a-quiver" Several of the shanties are about the life and troubles of black sailors.
