What happened

Cruise ship stocks fell on Monday following news of major sporting event cancellations. By the close of trading, shares of Norwegian Cruise Line Holdings (NASDAQ:NCLH) and Royal Caribbean (NYSE:RCL) were down 7.1% and 3%, respectively. Carnival's two stocks, Carnival Corporation (NYSE:CCL) and Carnival Plc (NYSE:CUK), also declined by more than 7%.

So what

Major League Baseball (MLB) postponed some games after multiple Miami Marlins players contracted COVID-19. The outbreak occurred despite the many precautions MLB is taking to protect players, and even as stadiums were devoid of fans. The news casts doubt on whether major sports leagues will be able to continue their seasons -- and suggests trouble for the near-term future of industries dependent on large gatherings of people. 

A cruise ship sailing at sunset.

If Major League Baseball can't protect its players, how will the cruise industry protect its customers? Image source: Getty Images.

The cruise industry has touted its collaboration with health experts as it attempts to safely resume sailing operations. Major cruise operators want to reassure customers that improved cleaning regimens and new social distancing measures will be enough to keep them safe. But MLB's recent issues with player safety amid the COVID-19 crisis suggest otherwise.

Now what 

If Carnival, Royal Caribbean, and Norwegian are unable to safely resume sailing operations during the coronavirus crisis, then they essentially become a bet on when an effective vaccine or treatment for COVID-19 will be developed -- and widely available. If you own these stocks, you're essentially wagering that these developments will occur before Carnival, Royal Caribbean, and Norwegian run out of cash. With vaccine development timelines uncertain at best, these cruise ship stocks remain risky bets.