Kimberly Davis has played some of the biggest stages in the world with Chic, the disco band co-founded by legendary guitarist Nile Rogers. She’s opened for Cher and headlined major festivals.

To hear her booming vocals on a recent Wednesday, you had to make your way to the Sunset Vista Ballroom at the Miami Beach Convention Center. Davis was trying to impress attendees of an annual cruise-industry convention in a showcase that resembled “America’s Got Talent.”

The ultimate goal: to land a gig on a cruise ship. Bookers now gather at the Seatrade Cruise Global convention every year to line up entertainment for cruises across the globe. More than two dozen acts—comedians, musicians, mentalists, magicians, dancers and jugglers—had 10 minutes each to prove themselves, which sounds harsh until you consider what cruise-ship audiences are like.

“On a cruise you have about three minutes to prove that you are worth staying for the next 40,” said Michael Linden, founder and chief executive of talent agency Oakdale Entertainment. “There’s so much to do on these ships that if they want to do something else, they very easily can, and people will get up from a show.”

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During the showcase, it’s not enough to sing well, tell a few good jokes or do one impressive magic trick. Guest entertainers are generally expected to perform multiple shows for each sailing, so bookers want to see some range.

When Broadway veteran Rachel Potter brought friend and fellow showcase act Omar Cardona out to sing with her, she told the audience they had developed an entire show of duets. “If you book us both, you get three acts for the price of two,” she joked, before they launched into a soaring rendition of “Into the Unknown” from the “Frozen 2” soundtrack.

Choosing the right song or trick is crucial. If an act comes across too niche, cruise lines that need to appeal to a broad audience will be turned off. Being too generic is similarly risky.

“You can only hear Journey so many times,” said Alex Crow, a booker with TAD Management, a talent agency.

Each act had 10 to 20 minutes to rehearse with the backing band and technical staff.

“You hope and pray they know what they’re doing,” said Avionce Hoyles, a New York-based singer and actor. His performance, a tribute to “the Kings of R&B,” went off without a hitch. “We definitely walked out of that room with meetings.”

Charity Angél Dawson, who has performed in Broadway productions of “Waitress” and “Chicago,” buttered up the crowd between renditions of songs popularized by Ella Fitzgerald and Aretha Franklin. “Cruising is my favorite way to vacation,” she quipped.

Katie Proctor, manager of variety entertainment at Norwegian Cruise Line Holdings , said she was particularly impressed by how one performer handled a technical issue gracefully.

“We want people who are going to be a delight to work with, who are going to be great with the crew, great with the technical staff and great with the guests,” Proctor said. “Just seeing how you respond in a moment of crisis, it’s wonderful.”

When a juggler dropped the ball, literally, he played it off with a joke. “How many times did I drop it?” he asked an audience member, before following up with: “How many times did I catch it?” (His agent said several bookers expressed interest in hiring him.)

Guest entertainers on a cruise reside in normal staterooms rather than crew quarters like other employees. They can eat in the dining rooms, swim in the pool and workout in the gym alongside other guests.

A one-week contract can pay thousands of dollars, which can help bridge the gap between land-based gigs.

Ivan Pecel, a world-champion juggler and comedian from California, has performed on ships since the age of 19 and about a quarter of his gigs are at sea. “In my 20s, Royal Caribbean paid my mortgage,” the 45-year-old said.

Hoyles said he’s used money from cruises to self-produce his own shows on land.

Historically, the Seatrade event was largely a showcase for other parts of the cruise supply chain, from shipbuilders to manufacturers of water-treatment systems. Then Ryan Stana, founder of entertainment company RWS Global, came up with the concept for the entertainment showcase. Seatrade organizers were on board but talent agencies were skeptical.

“People don’t like change,” Stana said. A handful of agencies signed on to the first year. A majority of the acts got bookings. This year, the showcase expanded to two days from one because so many agencies wanted in.

The performance space was decorated like a lounge, furnished with plush couches and chaises to approximate the vibe on a ship. A bar was set up in the back for spectators to grab drinks—performers congregated there after their sets to chat with bookers and agents.

One challenge for talent agents was that many of their top clients were on cruise ships during the showcase. Rick Hubbard, founder of Starbook Entertainment, had one performer who flew herself from Sweden for the occasion.

Pecel, the juggler, said it was an honor to be among the four acts from his agency to perform.

While some cruise lines expressed interest in working with him after his showing, he said he’s essentially booked through next year. “I have more work than I could take.”

Write to Jacob Passy at jacob.passy@wsj.com