It's OK to look out of your porthole, Carnival (NYSE:CCL) investors. Shares of the leading cruise-ship operator opened higher today, after the company posted better-than-expected fiscal second-quarter earnings.

The results aren't remarkable on their own. Revenue fell by 12% to just over $2.9 billion. Profitability took a 33% dip to $0.33 a share. However, analysts were willing to settle for just $0.29 a share on the bottom line.

Yes, it could have been worse. Savvy passengers are paying less for their cabins than they were a year ago. This was also the quarter when swine flu fears probably spooked more than a few potential passengers. Carnival had to rework many of its itineraries to steer clear of Mexican ports.

One can only imagine how bad things would have gotten for Carnival if energy costs hadn't plummeted since last summer's frenzied highs. Carnival had to pay only $304 per metric ton of fuel during the quarter, 43% lower than last year's tab during the same quarter.

Fuel is a big cost component for the industry, so you can already sense the trepidation, given the past few weeks of rising energy prices. Pesky spot prices for fuel finds Carnival now projecting to earn between $2.00 and $2.10 a share this year, short of its earlier guidance that pegged the company's year-end profits to be as high as $2.30 a share.

Hosing down guidance is typically a recipe for a tripped-up stock, but investors aren't stupid. They see what fuel prices have done over the past two months. The optimism for Carnival's stock this morning probably stems from its upbeat outlook. Booking volumes for the second half of the year are running 26% higher than they were at this point last year. Yes, these same cruise seekers are paying substantially lower prices than they were a year ago, but filling up its ships at a brisk pace is comforting.

This is good news for rival cruise-ship operators, such as Royal Caribbean (NYSE:RCL), NCL, and Disney (NYSE:DIS). It's also welcome news for the companies that rely on full ships, such as spa operator Steiner Leisure (NASDAQ:STNR), which runs the spas throughout Carnival's fleet. Casino-equipment specialists such as IGT (NYSE:IGT), WMS (NYSE:WMS), and Shuffle Master (NASDAQ:SHFL) may also catch a break here -- both onboard and in Caribbean gaming resorts -- to help offset stateside weakness in landlubber casinos.

As long as fuel prices keep in check and the economy doesn't slip back into a deeper funk, Carnival and its cronies will be just fine.

Steiner Leisure is a Motley Fool Rule Breakers selection. Disney is a Motley Fool Stock Advisor and Motley Fool Inside Value recommendation. Try any of our Foolish newsletter services free for 30 days.

Longtime Fool contributor Rick Munarriz is lucky to live in Miami, so he cruised with all four of the operators mentioned in the story. He owns shares of Disney and is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.