Still, on their latest and largest ships, both Norwegian and Royal Caribbean have been replacing revues with more relevant options. Some are slightly shortened versions of Broadway musicals—a little trip to the Great White Way in the middle of the great blue sea. They include such classics as Grease and Saturday Night Fever on Royal Caribbean, or more recent hits such as Rock of Ages and After Midnight on Norwegian. The shows of yesteryear barely even had a storyline; these have dialogue, upgraded costumes, and proper sets, just like their land-based counterparts. Some even feature members of the New York casts and production teams.

That’s just one strategy at play. Celebrity, Royal Caribbean's sister brand, is focusing on original productions, some with aerial acrobatics and high-tech effects—already, it has 18 such shows in its lineup. Elyria is its most daring: It’s a slightly risqué, avant-garde love story with choreography by industry veterans who have worked with Madonna and Kylie Minogue. The show was launched in 2015 on Celebrity Constellation and was an immediate hit.

And then there’s Edge, which hopes to push the boundaries further when it is launched in December 2018. With interactive elements reminiscent of the immersive theater phenomenon Sleep No More, the show will be different each time guests go. That’s an industry first, according to Becky Thomson-Foley, Celebrity's associate vice president of entertainment. People might go several times during a trip.

"The younger generation wants more choices than ever,” said Sarah Beth Reno, vice president of entertainment at Carnival Cruise Line, which has cut its main stage song-and-dance shows down to a bitesize 35 to 45 minutes, so people also have time to pursue such other options as stand-up comedy and live music.

"People want to walk around and experience everything that is available," agreed MSC's Glading. "I call it the buffet syndrome. They don't want to miss out on anything."

Jazz Hands in the Board Room
The recent fact is, shipboard stage experiences are translating to quarterly earnings.

For starters, some of the new entertainment comes with an extra price tag for guests, unlocking a brand-new revenue stream. (Even for cruises that charge for select activities and specialty dining, theater has always been all-inclusive.) MSC's Cirque shows are $42 (€35) with dinner, $18 without. Celebrity’s Eden show will also come with a cost, which has yet to be determined.

At Norwegian, which first introduced a dinner theater circus (created by Florida-based Cirque Productions) in 2010, the profits are obvious. The theater on Norwegian Breakaway, one of three ships with the show, holds 245; with nine shows a week at $39.99 (including dinner), performance revenue on that ship alone can hit $4.5 million a year.

"I remember people, even industry experts, saying, 'Oh my god, that will never work,’" said Celebrity’s Thomson-Foley, referring to optional shipboard specialty restaurants with an admission fee, something that has become an industry norm. "I wouldn't be surprised if that kind of leads that way with entertainment."

"We've definitely seen a shift in our guests telling us entertainment is a deciding factor for them," said Thomson-Foley, citing surveys from last year. And according to MSC’s Glading, "Entertainment isn’t the reason they book—it's the reason they come back."