What happened

Shares of the major cruise ship operators Carnival (NYSE:CCL), Royal Caribbean (NYSE:RCL), and Norwegian Cruise Line (NYSE:NCLH)all trailed the market last month. Each lost at least 13%, while the the S&P 500 slumped 9%, according to data provided by S&P Global Market Intelligence.

Those declines put each stock at a 52-week low, with 2018 losses standing at 18% for Royal Caribbean, 20% for Norwegian Cruise Line, and 26% for market leader Carnival. That compares with a broader market that shed 6% for the year. 

A cruise ship docked near an island.

Image source: Getty Images.

So what

None of these companies is struggling to meet sales projections these days. On the contrary, Royal Caribbean is expecting a record fiscal 2018 with net yields (a key industry growth metric) up about 4.5%. Similarly, Norwegian Cruise Line said in early November that strong demand during the peak summer sailing season powered it to record quarterly revenues and earnings.

Carnival also sounded an upbeat note, as it reported that net yields surpassed management's guidance for the third straight quarter and lifted results into record territory. "Our business model is more sound than ever," CEO Arnold Donald said in a conference call with investors, "having built into the fleet even greater ... resilience on top of an even stronger balance sheet."

Yet the stocks of the three largest cruise companies fell last month, in part because of broader global economic growth concerns. The bigger driver was an updated outlook from Carnival that spooked investors. On Dec. 20 -- the day of Carnival's third-quarter announcement -- its stock fell 10%, and dragged its peers lower as well.

Now what

Specifically, Carnival said in late December that vacation bookings are holding strong well into 2019 amid steady pricing, and that an unusually large proportion of its capacity has already been booked. That's good news, since it raises the likelihood of another record operating year. However, the pace of revenue gains is decelerating when compared to prior years. Revenue is on track to expand by about 1%, executives said, a marked slowdown from the roughly 3% annual gains made in each of the past two years.

Royal Caribbean and Norwegian Cruise Line should help clarify the growth picture for investors when they report their fiscal fourth-quarter results in the coming weeks. Given their stock slumps, though, Wall Street appears to be bracing for them to issue modest growth outlooks on par with Carnival's soft projections.

It's important to note that there's no concern about an industry slowdown right now -- the cruise giants are all about as optimistic as they could be about their opportunities. "While 2018 is proving to be another record year," Royal Caribbean CEO Richard Fain said in late October, "2019 is shaping up to be even better."

Meanwhile, even Carnival's lackluster growth forecast included financial targets that investors can celebrate. The company is planning to set more profit records in 2019 with help from the addition of several new ships to the fleet. Its peers are likely to have similarly positive comments about their earnings opportunities in the year ahead. In the meantime, cruise line stocks might continue underperforming the wider market -- at least until it becomes clear that the expected growth deceleration won't worsen into an actual slowdown.

Check out the latest Carnival, Royal Caribbean, and Norwegian Cruise Line earnings call transcripts.