Christopher Columbus's historic voyages have come alive through full-size replicas of two of his famous ships, the Nina and the Pinta, which sail the east coast and internal river systems of the United States as floating museums. On a recent visit to Charleston, school classes and tourists got a feel for what life would be like on such a ship, called a caravel, on a trans-oceanic voyage. Romantic, yes. Fun – rarely, according to volunteer educator Dave Zenk, who relates some of the hazards of