Cool Beans: I've been thinking along the same lines, wondering whether the sea shantie(s) under discussion here have any connection to the open-tuning instrumental piece that gave "Vastapol" tuning its name.

I can supply a little info, if I recall all this stuff correctly:

The tune is not Libba Cotten's original work; it was widely popular as a "parlor-guitar" piece in the mid-to-late 18th century.

The "Vastapol" guitar tuning is either Open-D (DADF#AD) or Open-E (EBEG#BE), which are essentially identical in terms of relative pitch and use the same fingerings, chord shapes, etc., except that one is two half-steps higher than the other. From standard tuning, you can either tune down to Open D or up to Open E. Among contemporary blues players, up-to-E is most commonly used on electric guitars, while down-to-D is more popular with acoustic intruments, which are a bit more fragile and are generally strung with heavier-guage strings, making it safer to decrease than to increase string tension.

The other common open tuning for the blues is "Spanish," named for a similar parlor-guitar favorite from the same era, "Spanish Fandango." For Spanish tuning, you have a similar pair of options to use either of two keys: tune down to Open G or up to Open A.

Back to the subject at hand: I would guess that the sea-shanty songs about Sepastapol might be completely different from the guitar-piece intrumental, if only because shanties are generally conceived and performed without instrumental accompaniment. Just my hunch...