A lot has changed about the business of putting people on boats and sailing them around the world since Gavin “Captain Stubing” MacLeod strode the decks of “The Love Boat” in the 1980s. Take size, for example. The Pacific Princess , the real ship that the fictional Stubing navigated to and from Puerto Vallarta each weekend, had capacity for all of 780 passengers, whereas today’s largest cruise ship, Royal Caribbean’s immense Harmony of the Seas , can accommodate close to 7,000 travelers. And it’s not just the size of the ships that has grown, but also that of the cruise...