Walk to dinner aboard Norwegian Cruise Line’s ship Norwegian Epic, and you might bump into SpongeBob SquarePants.

But the Nickelodeon network character, part of the standard on-board entertainment on some Norwegian ships, won’t invade your room and won’t cost you anything.

Not so for Mattel Inc.’s Barbie. To meet her on board a Royal Caribbean cruise ship, you’ll have to pay extra – but you’ll get to stay in a stateroom decorated in Barbie pink.

Starting in January, Miami’s Royal Caribbean Cruises Ltd. will offer passengers a special Barbie package that includes Barbie-themed activities and souvenirs. It will cost $349 per child – on top of the cost of the cruise. The two companies announced the Barbie package last week.

Called the Barbie Premium Experience, the package is aimed at girls age 4 to 11 and goes on sale next month for a limited number of ships. By March, Royal Caribbean plans to make the package available on all 22 of its ships, which visit the Caribbean, Alaska, Europe and other destinations.

The open seas are new territory for the El Segundo toy company, but the Barbie-branded packages are just the latest on-board entertainment offering from cruise lines that have been trying to bring in more passengers and revenue since traffic fell by as much as 25 percent during the recession.

The package includes a specially decorated stateroom with a Barbie blanket, pillowcase, tote bag and toothbrush, all of which guests can take home. But the heart of the package is the bevy of activities geared toward fans of the iconic doll.

Activities include a tea party during which girls will learn table etiquette while sipping pink lemonade and noshing on pink pastries. Add in a dance class where they’ll learn moves from the latest Barbie movie and a design workshop that culminates in a dance recital and fashion show.

All that pink could help Royal Caribbean attract new customers, said Teijo Niemala, publisher of Kerava, Finland trade publication Cruise Business Review.

“I think it helps for people who might be a little hesitant to go on a cruise in the first place,” he said. “That can be a gimmick for them to buy a cruise.”

Focusing on young girls also plays into Royal Caribbean’s strategy of catering to young and middle-aged families rather than to older, more luxury-minded customers.

Royal Caribbean and Mattel officials did not return calls for comment. The companies described the Barbie offering as a partnership when it was announced last week but did not disclose further details.

Barbie and Mickey

For kids, a standard cruise can verge on boring, even though the lines offer activities for children of various ages. But activities with characters or brands kids are familiar with is another thing.

“The kids just light up and say, ‘Hey, this is for me, on a cruise.’ So it makes sense with their demographics,” said Michael Driscoll, editor of trade publication Cruise Week in Brookfield, Ill. “I’ve seen this kind of activity on Disney cruises.”

Indeed, Barbie has plenty of company on the high seas. Walt Disney Co. operates its own fleet of four cruise ships that feature entertainment and appearances from Mickey Mouse, Donald Duck and other characters from the Burbank company’s catalog of animated films. And since the recession swamped the cruise industry, other lines have recently started working with brands and entertainment companies to provide on-board entertainment.

Since 2010, a handful of Royal Caribbean ships have featured actors dressed as characters from “Kung Fu Panda,” “Shrek” and other films produced by Glendale’s DreamWorks Animation SKG Inc. The ships also host screenings of DreamWorks Animation films. It’s all similar to the arrangement Norwegian Cruise Lines has with Nickelodeon.

But those arrangements don’t require passengers to opt in or pay an additional fee. Rather, costumed characters and movies or live shows are part of a ship’s standard entertainment offerings.

That makes Barbie an outlier. But Driscoll, the Cruise Week editor, said adding Barbie-themed amenities only for those willing to pay makes sense.

Disney and DreamWorks have wide audiences, but the appeal of Mattel’s Barbie is limited to young girls. So while Barbie may be Disney’s latest seafaring competitor, don’t expect Mattel to start a cruise line anytime soon.

“To have an entire Barbie cruise? Oh my gosh,” Driscoll said. “I think any parent would just go berserk.”