Let's not mince words here: If you're a recent shareholder of Norwegian Cruise Line Holdings (NYSE:NCLH), Carnival Corp. (NYSE:CCL) (NYSE:CUK), or Royal Caribbean (NYSE:RCL), you probably bought in because cruise line operators were among the hardest hit industries when the pandemic-fueled sell-off began in late February. If you managed to nail the bottom a few weeks later, you're probably sitting pretty right now -- but the same can't be said about the cruise line industry.

All three major cruise line stocks have more than doubled off their COVID-19 lows, and the news isn't all bad. Norwegian, Carnival, and Royal Caribbean have lined up billions in financing to keep them literally and figuratively afloat through the next few months. Roughly half of the passengers on cancelled sailings are opting for enhanced future credit instead of an outright refund.

The news gets dimmer after that. Let's go over some of the reasons why investors holding for continued gains may be in for some choppy waters. 

Two couples frolicking on the shore with a cruise ship behind them.

Image source: Getty Images.

1. No one knows when cruise lines will sail again

Cruise industry lobbying group Cruise Lines International Association announced on Friday that all of the leading cruise lines will cancel their sailings through at least Sept. 14. The industry will be working with the Centers for Disease Control and Prevention (CDC) to make sure all of the pandemic safeguards are in place when the industry resumes operations. Norwegian Cruise Line revealed earlier in the week that most of its ships won't be sailing again until October. 

Mid-September may seem extreme when the CDC's own No Sail Order is set to expire in late July. If there's one thing we've learned over the past few months, however, it's that this pandemic isn't afraid of moving goalposts. Does anyone remember when cruise ships were telling passengers that they would be sailing again by mid-April, then mid-May, followed by late June and early August?

Mid-September seems so far away that it has to be legit, but folks said the same thing about all of the other dates that came and went without a bon or a voyage. This is going to be a problem, and eventually, the diehard cruising customers that the industry will need to get rolling again will run out of patience.

2. Crew socks 

There's a grim side of the cruise line industry that isn't getting enough play in the press these days. There are currently more than 42,000 crew members on cruise ships waiting to be repatriated to their home countries. And they're not getting paid.

COVID-19 cases keep popping up, so these foreign workers who signed up to crew in order to provide better lives for their families back home are essentially unpaid prisoners on these floating Petri dishes. Can you imagine the class action lawsuits that will carry more weight than passenger mishaps, because at least Joe Q. Cruisefan got off the ship three months ago.

How many existing crew members do you think will be back in a few months or whenever the cruise lines can start safely sailing with paying customers again? Cruise lines are going to have to retrain its staff, and word-of-mouth in the countries where many of these crew members are from is as lousy as you can imagine. Even in a global recession, these will be some hard roles to fill in the future. 

3. Cruise lines need more money than you have patience

Cruise lines aren't facing a near-term liquidity crunch, but with dates getting pushed out -- and the likely profitability constraints in the new normal once the industry comes to terms with the CDC -- they'll eventually need more money. We saw the stocks get slammed a few months ago when they were desperate for cash. Carnival sold a ton of new stock at $8 a pop! 

Bulls will argue that the stock prices have recovered, but just wait until the collection trays start going around again. Just wait until paying passengers -- folks committing new money instead of getting 125% of what they paid earlier as an incentive to wait until 2021 -- dry up. 

We still don't know when COVID-19 cases will peak, and we don't know if cruise line stocks truly bottomed out three months ago. All bets -- or in this case, berths -- are off if the recession proves pesky. Some of the players with size and margin advantages may fare better than the rest, but this is still an industry that has a long way to go before it truly recovers. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.