My mother sang this to me in much the way that Deb describes it earlier (like 2011) but with the words:
See the boat go round the bend
Goodbye, my lover, goodbye.
She's loaded down with big fat men
Goodbye, my lover, goodbye.

Bye, Bye
Goodbye, my lover, goodbye.
For she's load down with big fat men
Goodbye, my lover, goodbye.

We are from the Gulf Coast of Mississippi. My great-great grandfather, born in 1850 sang it to her and explain it was about the movement of men from the south up the Mississippi river. They left well fed, came back starved. At least so goes the myth. Seems as though the tune and the essence of the song have been around even longer. I have been singing it to my children and grandchildren since their birth.