An "anthology of nonsensical and surrealist verse", _Straw in the Hair_ (1938), by Denys Roberts, contains an item labeled as,

"Mind how you Swing your Tail Negro SeaShanty."

I've not been able to see it, just the snippet on Google Books.

I'd guess this might have been drawn from an earlier publication—perhaps the version in The Crisis, since that one's dialect spelling would suggest "Negro" in ways that the two White sailors' recordings (for example) probably wouldn't.