After living in Antigua for almost 3 months, I have noticed a TON of people wearing black pearls (no, not strings a la Mikimoto...) but on leather ties or pieces of rope. Sailor-style I guess you could say. After complementing several friends on their necklaces and bracelets (PS I still dont have one of my own...) - I learned of the legend behind the trend.
Apparently, if you are at sea and in trouble, if you drop a black pearl into the ocean, it is a sacrifice to Poseidon, who will help you in your aquatic time of need. Similar to the Maori legend of the whalebone fisherman's necklace, which supposedly offers protection over water.
Before I leave the Caribbean I will gift a black pearl to myself!