Cruise line operator Carnival's (CCL) stock has sunk more than 10% since the giant Carnival Triumph ship went dead in the sea earlier this month, but smaller Miami-based cross-town rival Norwegian Cruise Line (NCLH) is riding high. Since Norwegian's initial public offering Jan. 18, shares have soared more than 60%. That makes it the best performing U.S. offering so far this year, according to IPOHome.com. Shares of the second-best performer, 3D