Pronunciation Realization

Where do you place the accent in the word "Caribbean"? Per se, I normally accent it as ca-RIB-be-an. But, I realized, in reference to the Johnny Depp vehicle, I pronounce "the Pirates of the CA-ri-BE-an". And when I think about it, I realize that doing so makes the phrase iambic (yes, with a femine rhyme, which is why there's an extra syllable on the end). Why?

Robert Frost said writers in English have a choice between two meters: strong iambic and weak iambic.

I guess readers in English only have those two choices, as well.