It's a great film...I used to use it in my teaching all the time.

The whole of Folkstreams is a great site...you should check out all the films there.

Finally, as others have said, this film as such presents no evidence for the "origins of shanties" as "negro (slave) work songs." If anything, it suggests what we already know: work songs were a major component of the blues. Phrases like "Birmingham ain't no ham at all
You oughta see that ham up my gal drawer" sound not a bit like shanties....