Mac the Black was a pirate in the Caribbean Sea in 1697. His ship was previously the flagship for the Spanish Armada, which had been chasing him across the Caribbean. He had ties to Captain Hook and Long John Silver.
Mac encountered Marty McFly and Verne Brown while Marty was claiming to be him to impress the ladies. A scurry to find his impostor around the islands resulted in Marty being forced to work on his crew and the eventual destruction of his ship when a cannonball was fired vertically and came back down.