Christina Kerby was corralled aboard a massive luxury cruise ship, charting a meandering course somewhere in the South China Sea, when she began thinking about the apocalypse.

Luckily, the WiFi on Holland America’s MS Westerdam was plentiful. She tapped out a tweet.

“Here’s a science fiction plot line for ya,” she wrote. “Amidst a global epidemic that wipes out the earth’s population, it’s up to the people aboard one cruise ship — the only safe place on earth — to repopulate the planet. **Passengers onboard the #Westerdam begin eyeing each other nervously**”

It was an idea befitting her new dystopian reality — but instead of a sci-fi thriller, she was going for lighthearted comedy. The way she saw it, there wasn’t much else she could do, as her long-planned vacation was ensnared in a global frenzy over a fast-spreading disease and the story of her cruise ship had spiraled into international news.

Kerby boarded the ship in Hong Kong on Feb. 1, but hundreds of other passengers had been cruising since Jan. 21, riding a route that was supposed to ferry them north, from Cambodia to Japan. Soon after Kerby got on, plans began to change.

Four times the Westerdam tried to dock at ports across East and Southeast Asia, and four times it was turned away, rebuffed by governments frantically trying to protect their countries from the spread of coronavirus, now known as covid-19. Authorities are wary of cruise ships after infections rose aboard the Diamond Princess, which is quarantined at a port in Yokohama, Japan. Strict new measures have also banned from cruise ships anyone who has recently traveled in China.

Even after the cruise line decided to cancel the rest of the trip, it struggled to find a country nearby that would allow its legions of passengers and crew to disembark and catch flights home.

Holland America tried to reassure officials in Japan, Taiwan, the Philippines and Thailand: The ship is virus-free, the company said again and again, with no known or suspected cases on board. On Monday, the crew told passengers they’d be able to get off in Bangkok, the cruise aborted but fully refunded.

But by the next day, they’d been told once more they were unwelcome. They’d have to keep floating, with no end in sight.

That’s about when Kerby, a 41-year-old who works in health-care communications, decided to start tweeting.

“I felt like it was really important to dispel some of the fears and misconceptions about what was going on in the ships,” Kerby told The Washington Post in an interview from the ship. “I was reading a lot of really scary and negative media reports, and I thought, this is not giving an accurate picture of what’s going on, so I wanted to bring some truths and some positivity to the mix.”

Because life aboard the ship bore little resemblance to the dire plot Kerby outlined in one of her tweets — at least for the passengers who paid a premium to ride the stately Westerdam, recently remodeled with a new bar and something called the Music Walk, which includes a “Lincoln Center Stage” and a “B.B. King’s Blues Club.”

Her Twitter account became a live, public diary of the unexpectedly adventurous cruise. She has posted two dozen times, sharing photos and videos, opening a window into the strange pattern of life on board.

The ship was stranded, on the verge of a geopolitical crisis, but the revelry did not stop.

The U.S. ambassador to Cambodia also tweeted his thanks. Kerby posted a video of passengers bopping to a cover of Bill Haley’s “Rock Around the Clock” in celebration. When she woke up Thursday, local time, Kerby could see land. The ship was anchored near Sihanoukville, and the crew said they’d be off soon, after a health check.

As the ship made its way into port on Thursday, Kerby diligently live-tweeted its progress. She wondered whether her husband would agree to buying a waterbed once she returned home, writing, “Not sure I’ll be able to sleep on dry land.”

She reported that the passengers remained upbeat — even though the muesli had run out at the buffet. Around dinner time on the ship, she noted that she was feeling rebellious and had decided to wear sneakers in the dining room.

The captain had said the clearance process was going smoothly, she wrote, but taking longer than expected. Not that she minded.

“People seem relieved to have time for more swimming and ice cream onboard,” she wrote.

And then, early Friday, Kerby signed on to share another series of updates: The Westerdam had been given the all clear.

The cruise to nowhere had arrived, and its passengers were finally coming ashore.

Read more:

How cruise ships are handling mass onboard quarantines as the new coronavirus spreads

Ten passengers infected with coronavirus on quarantined cruise ship with thousands aboard

Cruise lines ban anyone who has recently been to China as coronavirus fears spread