First, there was the Diamond Princess, stranded off the coast of Japan as the coronavirus infected hundreds of passengers. Then the Westerdam, circling in the sea for days with nowhere to dock. Then the Grand Princess, the Costa Luminosa and the Zaandam.

Cruise ships have been a focal point of the coronavirus pandemic from the beginning, widely blamed for a series of major outbreaks that spread the disease across the world.

Now, the companies that own those ships face a potential financial catastrophe. With most international travel halted, they have virtually no revenue. They have become symbols of deadly contagion. And despite assurances from President Trump, they were left out of the $2 trillion stimulus package Congress passed last month. While analysts say the major cruise lines have enough money to survive at least another six months, the companies are scrambling to line up new financing in anticipation of a slowdown that could last even longer.

The Carnival Corporation, which serves nearly 11.5 million travelers a year, or roughly 50 percent of the global cruise market, is at the center of the crisis. Over the last couple of months, the company has had highly publicized outbreaks on several of its ships, including the Diamond Princess and the Zaandam, which has been attempting to unload sick passengers in Florida.

Since the beginning of the year, the company’s share price has plummeted more than 80 percent, though on Monday it rose sharply — to $10.21 a share — after Saudi Arabia’s state investment fund said it had acquired a stake in the company. And last week, Carnival, which has already drawn on bank credit lines, began an effort to raise $6 billion by selling stock, bonds and other securities. It was selling some of those bonds with a suggested 12.5 percent interest payment to investors, a strikingly high figure.

In an interview, Carnival’s chief executive, Arnold Donald, said the sale would generate enough cash for the company to survive without revenue for the rest of the year and into 2021. He added that Carnival hoped to take advantage of stimulus programs in other countries where it operates, like Germany, Britain and Australia.

“If you run out of cash, you lose the company, and we can’t live with that,” Mr. Donald said. “So we want to make sure we’re prepared for an extreme case.”

Last week, a voluntary one-month suspension of cruise travel became much longer, with some companies canceling voyages scheduled for October and November. Mr. Donald acknowledged that it was a precarious moment. The high interest rate on the debt deal “is absolutely going to be a challenge to us,” he said.

“It’s not fun to be floating equity at the share price it is,” he added. “It’s very disappointing.”

Before the equity offering, Goldman Sachs, JPMorgan Chase and Bank of America had been working to put together a debt deal for Carnival that would offer some investors a potential return in the high teens, according to two people familiar with the discussions. Bankers pitched the deal to hedge funds and private equity investors, some of whom passed on it because of concerns about the company’s long-term viability.

The two major cruise lines besides Carnival — Royal Caribbean and Norwegian Cruises — are also looking for cash. Norwegian has tapped an existing $1.55 billion credit line. In March, Royal Caribbean secured a $2.2 billion loan, using its ships as collateral.

Of course, the ultimate fate of Carnival and the rest of the cruise industry depends on how long the pandemic lasts. And even if the companies survive, it could take years for them to fully recover.

“It wouldn’t surprise me to see the industry redrawn in some ways,” said Ross Klein, a sociologist at Memorial University of Newfoundland who studies cruising. “Perhaps some companies disappearing, others being taken over, seeing ships being retired.”

In February, cruise ships became an early symbol of how rapidly the coronavirus could spread in confined spaces, when more than 700 passengers on the Diamond Princess became infected as the ship idled off the coast of Japan. As social distancing grew more common in February and early March, cruises were among the first activities Americans started avoiding.

Still, industry experts hope that hard-core cruise fans will come back relatively quickly once the pandemic ends, though even the optimists acknowledge that getting people to go on cruises for the first time will require steep discounts and aggressive marketing. Another challenge: About one-third of cruise passengers are 60 years old or over — a group at higher risk of serious infection that might be reluctant to risk exposure.

For Carnival, the initial coronavirus outbreak in Asia led to weeks of criticism, as the company fumbled its response to the situation on the Diamond Princess. Another of its ships, the Grand Princess, had a cluster of infections last month as it headed to California.

Mr. Donald defended Carnival’s response to the pandemic, including its decision to continue sailing in early March, as the scale of the global crisis was becoming clear. (Carnival eventually suspended global operations, but it still has four ships at sea.)

“We don’t try to play God. We don’t try to play government,” Mr. Donald said. “We comply. We listen to what people say we need to do.”

Last month, Mr. Donald and other industry leaders held talks with the White House coronavirus task force led by Vice President Mike Pence. In those conversations, Mr. Donald said, he pushed for a federal loan guarantee that would allow the cruise companies to obtain funding at lower interest rates. And Micky Arison, the chairman of Carnival’s board, has had several calls with President Trump, who last month described the cruise lines as “prime candidates” for federal support.

But under the terms of the stimulus package Mr. Trump signed into law, the major cruise lines did not qualify for funding because they are incorporated outside the United States, which largely exempts them from paying federal income taxes.

A piece of that package “would’ve been nice to have,” said Felicia Hendrix, a cruise analyst at Barclays.

Still, she said, the cruise companies are in a good position to weather the crisis, partly because operating costs have plummeted. “You’re not feeding a full ship’s worth of people,” Ms. Hendrix said. “You don’t have a full crew. You’re not using the full level of fuel.”

And unlike neighborhood restaurants and other small business that are now on the brink of collapse, the cruise lines started the crisis with healthy balance sheets. At the beginning of the year, Carnival had $518 million in cash on hand, Royal Caribbean had $243.7 million and Norwegian had $252.9 million.

But because of the crisis, Carnival and Royal Caribbean have laid off or furloughed contractors, while Norwegian has cut salaries and moved some employees to a four-day workweek. The impact of the cruise shutdown has also rippled across the economy, hurting travel agents, taxi drivers and performers.

Last month, one of Carnival’s nine cruising brands, Carnival Cruises, told dozens of entertainers who perform on its ships that it would not pay them for canceled bookings. Then a few days later, the company said it would pay them after all. Then it announced a new complication — the payment would come at some point in the next 60 days rather than the usual two weeks.

“This billion-dollar company took this burden and moved it from themselves to us,” said Steve Burr, a 52-year-old comedian in Tampa, Fla. “I’m driving Uber now trying to pick up a dime where I can and desperately trying to file for unemployment.”

For the last few weeks, Mr. Donald has been working from his condominium on Miami Beach. He has the place to himself — his wife is on one of the ships still at sea.

Sometimes, he takes walks along the beach, marveling at the emptiness. “The pigeons actually looked confused because there were pigeons and no people,” Mr. Donald said.

But mostly he dwells on the line of idle cruise ships anchored at shore, with nowhere to go. “They’re standing right out there as I look out,” he said. “It’s very surreal.”

Matthew Goldstein contributed reporting.