It all feels a bit like deja vu, but the cruise industry is soldiering on as the Omicron coronavirus variant makes its presence felt at sea as it has on land.

In the early days of the pandemic, cruise ships became synonymous with Covid-19, as virus-hit vessels struggled to disembark passengers and crew. The cruise industry subsequently shut down for months, and while some European journeys recommenced in summer 2020, cruise ships didn't navigate US waters for another year.

When cruising did return, it was with stringent rules designed to mitigate the impact of Covid-19. This combination of mask-wearing, testing, vaccinations and increased medical facilities led Martyn Griffiths of industry body Cruise Lines International Association (CLIA) to tell CNN Travel in June 2021 that cruise ships were "one of the safest vacation environments available today."

Vessels weren't guaranteed virus-free, CLIA said, but the goal was to avoid severe illness and major disruption.

Six months later, as the highly transmissible Omicron spreads around the world, the situation seems a little more precarious.

Health and safety

"There is no doubt that the Omicron variant has cast a great deal of uncertainty into the travel and tourism sector overall," said Bari Golin-Blaugrund, another CLIA representative, in a recent CNN Travel interview.

Golin-Blaugrund made the case that while there have been several recent reports of Covid outbreaks on board the world's cruise ships, Covid cases are a "minority."

She said cruise lines remain confident in their health and safety measures, adding that these measures "are proving successful to virtually eliminate severe outcomes," as hospitalizations are minimal.

While fully vaccinated people are not immune to Omicron, Dr William Schaffner, an infectious diseases expert at Vanderbilt University, told CNN Travel that "booster shots improve the individual's protection against getting severe disease."

However Schaffner cast doubt on cruise lines' ability to control the spread of the virus on board, even with fully vaccinated passengers and crew, and additional levels of protection in place such as mask wearing and regular testing.

"It's not so clear how much boosting helps to diminish transmission, especially in such high potential transmission circumstances where people are so close together for such prolonged periods of time," he said.

Schaffner suggested any traveler who chooses to go on a cruise at present is likely aware of the potential risk and uncertainty, and will have weighed this up before boarding.

"I think they must share a certain confidence in what it is that both the cruise line industry, as well as their fellow passengers are doing in order to mitigate the risk," he said.

"And to a degree, they must feel themselves if not invulnerable, but likely to survive an infection. I mean, you would have to go through that kind of thinking before you decided to go cruising at the present."

Passengers disembarking the Celebrity Apex cruise ship in Crown Bay Marina in Charlotte Amalie, Saint Thomas, U.S. Virgin Islands, on January 19, 2022.

Certainly, unlike the passengers caught up in the Covid fallout of Spring 2020, those on cruise ships today are aware Covid-19 is a risk, in the sense that they could catch it and fall ill, or the virus could disrupt travel plans.

British traveler Joy Bailey experienced first-hand what happens during a Covid outbreak at sea when she flew with her husband from the UK to Florida to embark on a Christmas/New Year sailing on board the Celebrity Equinox in late 2021. The 2,850 passenger capacity vessel operated by Celebrity Cruises was sailing at 60% capacity.

Bailey told CNN Travel that she accepted "we're all going to get Omicron at some time," but hoped the decreased capacity and other measures enforced by Celebrity Cruises would mitigate the likelihood of her catching the virus on board.

From the outset, Bailey said she was a little uncomfortable as many passengers ignored Celebrity Cruises' face mask policy.

Five days into the journey, she tested positive. Bailey spent the rest of the voyage confined to a quarantine cabin, joined there by her husband when he tested positive a few days later.

Isolating on the ship was "good and it was bad," according to Bailey.

The couple had a balcony cabin, so they could sit in the sun to pass the time. But they also describe waiting an hour on the phone to order meals.

When the voyage came to an end, Bailey told CNN Travel she was advised by Celebrity Cruises to head to a hotel she and her husband had pre-booked in Fort Lauderdale. The couple now faced a longer stay there before their return to the UK, as Bailey's husband was still isolating.

The cruise company told them to contact its "care team" on shore to get assistance re-arranging their flight, but according to Bailey, the couple struggled to get through to the number provided. When they did get through, they were told no help could be given because they weren't in Celebrity's designated isolation hotel.

"That was a crazy moment," said Bailey. In the end, they contacted their travel agent, who contacted Celebrity directly and changed their flight.

Celebrity paid for Bailey's stay in isolation. She and her husband were also offered up to $100 a day to spend on food. The cruise line is also covering the days they lost on the cruise itself.

"All in all, it wasn't too dreadful," said Bailey. "But the experience with Celebrity on the ground in Miami was awful. I think they were just overwhelmed."

This was Bailey's first cruise in the wake of Covid. Pre-pandemic, she would cruise every couple of years. Testing positive on board hasn't put her off traveling by sea, she said, but she'd like to see better coordination between the ship and the ground staff.

"We deeply regret this guest's experience as it was not in keeping with the high levels of care and service we pride ourselves on providing," a Celebrity Cruises spokesperson told CNN Travel in response to Bailey's claims.

"We quickly learned from the experience and have since introduced a dedicated concierge team to ensure the needs of any guests impacted onboard are met every step of the way."

Changing itineraries

Daniel Jay Park on board the January 9 sailing of the Norwegian Gem, which unexpectedly became a "cruise to nowhere."

The current Omicron chaos has also led cruise lines to cancel sailings, sometimes mid-voyage.

Passenger Daniel Jay Park said the unexpected termination of his January 9 sailing on board the Norwegian Gem -- a 294-meter-long ship which was sailing with a reduced capacity of 800 -- didn't impact his enjoyment of the voyage.

The ship set sail from New York before cutting its voyage short at the Caribbean island of St Maarten. Park told CNN Travel that when letters were sent to cabins to inform of the cancellation, passengers were "confused" and "a little frazzled."

While Park and his husband were disappointed to miss the scheduled Caribbean ports, they decided to make the most of the circumstances, assured by the fact that everyone on board would have been vaccinated.

"I trust science and technology," Park told CNN Travel.

The letter also stated that travelers would be entitled to full refunds.

Passengers were still able to freely roam around the ship and enjoy activities, said Park. Essentially, the voyage became a "cruise to nowhere" -- something some many have opted into voluntarily in recent months in countries including the UK, Singapore and Hong Kong.

Daniel Jay Park and his husband made the most of their time on Norwegian Gem.

Park said the experience didn't put him off cruising, he also has nothing but praise for the way Norwegian Cruise Line handled the unexpected situation.

"We were just having so much fun and they were so good to us," he said. "And now that the cruise was free, I'm like, 'Oh my god, we have all the money back on our credit cards, let's go again."

Park said that the cruise line didn't give an exact reason for Norwegian Gems' cancellation.

A spokesperson for Norwegian Cruise Line told CNN Travel that Norwegian Gem was impacted by the "current fluid public health environment" which means the cruise line must "make tough decisions and often times with very short notice."

The spokesperson confirmed passengers were refunded with their original form of payment, and also provided with $100 onboard credit per stateroom and given a "Future Cruise Certificate" valued at 50% of the voyage fare paid.

"The rapid spread of the Omicron Variant around the world may shape how some destination authorities with limited medical resources view even a small number of cases, even when they are being managed with our vigorous protocols," said CLIA's Golin-Blaugrund.

She added that CLIA is not aware of any situations in which passengers have been prevented from disembarking at their final destinations.

Crew perspective

Crew members on board the Norwegian Pearl, which returned to Miami after only one day at sea in early January 2022.

Crew members working on cruise ships right now face an uncertain day-to-day. CLIA's Bari Goin-Blaugrund confirmed reports that sometimes Covid-hit crew are transferred to specific quarantine vessels.

"CLIA ocean-going member lines have been utilizing out-of-service ships for crew members who have tested positive for Covid-19," she said. "Crew members are then monitored by the ships' medical team during the course of their 10-day quarantine before returning to their assigned ships."

A crew member working on a ship operated by Regent Seven Seas in the Caribbean told CNN Travel that while they felt relatively well-protected from Covid-19, there are other stresses involved in working on board during the pandemic -- including dealing with schedule changes.

"A lot of our guests actually, they're just enjoying the process," said the crew member, who spoke on condition of anonymity as they were not authorized to speak to the media. "But some, they start to complain, and of course it affects the crew because if, during your work, during the service on a daily basis, you have to calm them down, it's not very pleasant."

The crew member, who spent four months sequestered at sea during the spring 2020 Covid outbreak, said they were prompted to sign up again in October 2021 partly due to a lack of hospitality jobs on land.

They said they started their present contract before Omicron hit, and subsequently agreed to an extension to help cover staffing shortages.

While there was no written guarantee, the crew member hoped the cruise line might allow staff to disembark for shore leave. So far that's not been permitted.

"It's illogical, because the safe bubble is already destroyed when some people go ashore," the crew member said, adding that not being allowed off board impacts crew mental health.

Regent Seven Seas and its owner, Norwegian Cruise Line Holdings, did not immediately respond to request for comment.

Looking to the future

Golin-Blaugrund is hopeful for a brighter cruising future -- CLIA's goal is all ocean-going cruise ships back in operation by summer 2022.

Cruise ships in US waters were previously subject to Covid-19 rules enforced by the US Centers for Disease and Protection (CDC). This has now become optional, but Golin-Blaugrund said most cruise lines will likely continue to work with the CDC.

Meanwhile infectious disease expert William Schaffner is cautiously optimistic about how Covid-19 might develop in 2022 -- at least in countries with readily available vaccines -- as boosters and rising natural immunity could render the virus endemic rather than pandemic.

"If that occurs, then the risk for all kinds of congregate activities, including cruising would go way down," Schaffner said.

Still, added Schaffner, cruise ships by their nature travel across the world, stopping in different ports -- and each destination may be in a different stage of its Covid-19 journey. The cruise ship population -- both passengers and crew -- are also international.

Cruise ships could continue to be navigating tricky waters for some time yet.