Uncertain whether pirate talk be authentically or mockingly archaic

@ZhanlongZheng asked the following question on ELL:

Barbosa: I defended her mightily enough, but she be sunk nonetheless.

Jack Sparrow: If that ship be sunk properly, you should be sunk with it.

— Pirates of the Caribbean: On Stranger Tides

I don't understand why be is used here twice. Is it archaic? Why use this form?

I think that the second instance of be could be present subjunctive in the third person, with the subjunctive being appropriate due to it being in a conditional clause. I'm less sure about the first instance.

No doubt, use of the subjunctive has fallen out of favor, and nobody talks like that today. However, I'd like to know, were these conjugations of be ever considered proper archaic English, or are they strictly pirate talk invented by Disney screenwriters?

Solution 1:

Y'arr, it be as fake as a keg of rum-flavoured water:

• From the seahorse's mouth (Writers Guild of America): Aye Before E, Except After Sea
• National Geographic: "Talk Like a Pirate Day" Busted: Not Even Pirates Spoke Pirate

Or just ask skeptics.stackexchange.com.