Looking to convince Chinese tourists that a ship can be a holiday destination and not just a way to get there, the world's leading cruise lines are spending billions of dollars on flashy new vessels and quirky on-board services. Carnival Corp and Royal Caribbean Cruises Ltd are trying to pique interest with China-centric attractions such as a menu inspired by an ex-president. They are also tapping a national penchant for education with classes ranging from foreign languages to silver service. Drawing cruise lines to China is the prospect of $11.5 billion in sales come 2018 compared with $6.8 billion last year, according to researcher Euromonitor. The market will soon be the second-biggest and could eventually surpass the United States, industry executives said.