There is much in chanties that has no relevance to the sea. To look for any where it doesn't exist is futile. We are well aware that seamen utilised all sorts of material to use as chanties, and one with an easy, catchy, popular tune would soon be adopted/adapted. Surely a chantyman, and indeed the crew, would experiment with any new material and adapt as necessary, hence the different usages and metres. As many of the chanties obviously came aboard via the river trade into the Gulf, there's no reason to believe this one wasn't among them.