NEW YORK (TheStreet) -- The Greek economy is burning while Chinese stock prices are plunging, a wicked undercurrent that could sink the financials and stock prices of major cruise line operators.

According to trade association Cruise Lines International Association (CLIA), direct cruise line industry spending in Greece stands at about $620 million annually, a majority spent on wages to support 11,000jobs in Greece. Greece is Europe's seventh-largest beneficiary of direct cruise line industry spending. In 2013 and 2014, spending onthe cruise industry in Greece rose by about 10%, estimates CLIA.

If Greece exits the European Union, a prospect raised over the weekend with its "no" vote on more painful austerity measures, vacationers could choose to avoid the country for fear of being exposed to social unrest and having a poor travel experience. For cruise line companies, that uncertainty could have several profit-busting effects. 

First, for companies such as Carnival Cruise Line (CCL) - Get Report and Royal Caribbean (RCL) - Get Report, Greece may become tougher to market this year and next year to prospective travelers, possibly triggering the need to discount European vacation packages. Second, cruise ships could be diverted from Greece in the near term, which would come at a considerable expense to cruise companies in areas such as fuel and personnel.

But with the potential for Greece to leave the EU, it's the broader impact to European travel and operations that likely has cruise line execs the most worried.

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According to CLIA, 16.4 million European residents booked a cruise in 2014, representing a 0.5% increase over 2013. That tally accounted for 30% of all cruise passengers worldwide.

Norwegian Cruise Line (NCLH) - Get Report, Carnival, and Royal Caribbean declined to comment on the impact of Greece and their plans, if any, to adjust itineraries. Signs of problems in Europe have already started to emerge, however.

Roughly 5.85 million passengers embarked on their cruises from European ports in 2014, a 3.6% year over year drop, per CLIA data. Carnival CFO David Bernstein has said that "geopolitical risk" in Greece and overall economic weakness in Europe has led to "some challenges on the yield side this year." 

Carnival's Costa is Europe's largest cruise line based on guests carried and passenger capacity. In an interview with TheStreet on June 23, Carnival CEO Arnold Donald conceded "Europe is not up as much as North America," referring to revenue yields, or the amount of net revenue generated per day a ship is out at sea. Donald was quick to point out, though, that yields in Europe are not down overall.

As for China, the situation for the cruise lines is a little different -- unlike Greece, the Chinese economy continues to grow. But the rout in Chinese equities could cause affluent Chinese to put off taking a cruise this year and in 2016, just as the cruise line companies are devoting their newest ships to the region.  That could hurt returns on investment on the fancy new ships now sitting in Chinese waters. 

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About $2.7 trillion in value has been destroyed since the Chinese stock market peaked on June 12. That represents six times Greece's entire foreign debt, or a whopping 11 years of Greece's economic output. Prior to the latest stock rout, CLIA estimated the number of cruise vacationers would top 8 million per year by 2020 in China. In 2014, 700,000 out of China's 110 million leisure travelers booked a cruise.

Carnival, which is profitable in China according to Donald, has four vessels in the market in its Costa and Princess lines, and will debut another in 2016. The company projects 2.5 million passenger cruise days in China this year, jumping to 4 million or so next year.

Royal Caribbean, which is competing in China with its new Quantum of the Seas and three other ships, will notch about 1.8 million passenger cruise days in 2015. In 2016, Royal Caribbean's new Ovation of the Seas will be based in China, as well.

Norwegian Cruise Line has no ships in the country, but has been exploring an entry.

Shares of the cruise line operators have been on a hot streak the past year, as an improving U.S. economy has more Americans booking pricey cruise-based vacations and China is seen as the next big growth market. Carnival, Royal Caribbean and Norwegian Cruise Line have seen their stocks surge by 32%, 38% and 71%, respectively, in the last year.

With the respective problems in Greece and China grabbing headlines, investors may revisit their positions in cruise line operators ahead of what could be more subdued earnings outlooks later this year.