Roy Harris once told me, "When all else fails, sing Essequibo River". He just makes up verses as he goes along, which I think is more in the true tradition of shanty singing than learning a fixed set of archival verses from a book. I've added Martin Simpson's when I sing it, and one of my own:

Essequibo Mary, she's the queen of Marys all
Buddy ta-na-na, etc
Goes running to the docks when she hears the sailors call
Buddy ta-na-na, etc.