Royal Caribbean Cruises Ltd. is best known for high-energy innovation, with onboard rock-climbing walls and surf pools on its Royal Caribbean ships and cutting-edge dining on its Celebrity brand. Thursday the Miami-based company announced it will purchase a 66.7 percent stake in Silversea, a privately owned ultra-luxury and expedition cruise leader. For luxury vacationers, the union will likely bring expanded offerings and greater value for money, said experts. The deal unites "two com