One by one, the passengers pulled down their masks and rejoiced as they cleared security and health screening to board the first cruise ship sailing out of North America since the pandemic was declared in March of last year.

One woman threw her bag on the floor and started shimmying to the Caribbean calypso beat playing in the welcome hall. Another triumphantly bumped fists with a crew member before giving him a hug, while an older man stood still and gazed at the elated guests, his eyes welling up as he processed the reality of being back on a cruise, one of over 400 he has taken in his lifetime.

“We’re back, we’re home,” one passenger yelled as she entered the vessel. “Welcome back ma’am,” a crew member responded with a gleaming smile. “We’ve missed you.”

For many of the 600 or so passengers embarking on the Celebrity Millennium, operated by Royal Caribbean’s Celebrity Cruises, from the Caribbean island of St. Maarten on Saturday, this was the moment they had dreamed of over the last 15 months, as cruise ships remained docked in ports, even after vaccinations rolled out in the United States and people started to travel again.

For the ship’s 650 crew members, the event was equally joyous, bringing relief after a grueling year without work or a steady income.

“It was very difficult to survive at home for 14 months,” said Donald Sihombing, a 33-year-old stateroom attendant from Indonesia. “I feel very happy and lucky to be back. There are still so many people who have to wait for cruises to start in America to be able to work again.”

The major cruise lines are preparing to restart operations from United States ports this summer, with Celebrity Edge poised to be the first, sailing out of Fort Lauderdale, Fla., on June 26, with all crew and at least 95 percent of passengers fully vaccinated, in accordance with guidelines issued by the Centers for Disease Control and Prevention. But those plans could be disrupted if Florida does not exempt the cruise lines from a recently enacted state law banning businesses from requiring proof of immunization from people seeking to use their services.

Celebrity is currently in talks with the C.D.C. and state authorities in Florida and is optimistic that a solution will be reached in time for the sailing. Susan Lomax, the company’s associate vice president for global public relations, said it would continue to offer vaccinated voyages to ensure the health and safety of guests, crew and local communities in destinations visited.

Here are some takeaways from the first major international cruise with American passengers since 2020. The itinerary for the seven-day cruise from St. Maarten included stops in Barbados, Aruba and Curaçao.

To board the Celebrity Millennium all adult passengers were required to fill out a health questionnaire and show proof of vaccination and a negative PCR test. In addition, St. Maarten requires visitors to present a printed copy of its own health screening document, which must be authorized ahead of time.

The check-in process starts at home, through Celebrity’s app or website, which allow you to scan your passport, fill out paperwork and book a time slot for boarding. Once all the steps are completed, the system generates an express pass designed to minimize contact and speed up boarding procedures. At the departure hall, the pass was scanned and vaccination and test certificates were reviewed by staff, then guests were allowed to enter the ship.

But be prepared for surprises. Initially, Barbados, the first port of call, required visitors to present a negative Covid test taken 120 hours before departure. But it changed the requirement to a test taken within 72 hours, meaning that some passenger’s results would have expired by the time they arrived.

Celebrity had a testing station set up at the departure terminal and provided free rapid antigen testing that produced results within 20 minutes, allowing guests onboard.

Those who cruise regularly will be familiar with the muster drill, a safety exercise that usually requires passengers to gather in a cramped muster station and watch a safety demonstration that takes 30 minutes or more. One passenger described the process as “miserable.”

This week, Celebrity debuted its new e-muster system, which allows passengers to take a tutorial on their electronic devices, showing them how to wear life vests and familiarizing them with the sound of emergency signals. Once on board, passengers simply walk to their designated muster area and are given a small sticker to put on their room card to show that they have completed the process.

Upon embarkation, guests were allowed to go straight to their rooms. (Before the pandemic, they had to wait until 1 p.m.) All the rooms were stocked with hand sanitizer, face masks and were disinfected each day.

All the ship’s amenities, including the gym, spa, casino and theater, were open and fully functioning, though the ship was operating with about a third of its normal passengers. To cut down on contact, rooms can be unlocked using Celebrity’s app on your phone and all restaurants, activities and shore excursions can be booked through the app.

Face masks were not required for cruise guests because of the vaccination requirement, but the crew was expected to wear them while on duty, a rule that will be reviewed after the inaugural sailing.

Both PCR and antigen Covid tests were complimentary and available onboard.

Some cruise fans feared that cruise buffets would be abolished in the post-pandemic era, but in the Oceanview Café on the tenth deck of Celebrity Millennium, the buffet stations were in full force. The main difference was that the food was served by crew members.

When guests enter the restaurant, they must first wash their hands at the basins in the entrance — a requirement even before the pandemic. Then they can stroll from station to station pointing at what they want for the staff to portion out.

The new system worked well with the ship at 30 percent capacity. Servers kept up with demand and there was no overcrowding at the stations, but were the vessel to sail with its full complement of 2,210 guests, the experience would likely be more hectic.

Some guests had anticipated a drop in food quality because of the financial hit cruise companies have taken since the start of the pandemic last year, but most said Celebrity had maintained a high standard of food and service.

“We have invested even more into our food and beverage services and enhancing our amenities across all levels,” said Lorenzo Davidoiu, the associate vice president of service excellence at Celebrity.

After a frustrating year of booking multiple cruises only to have them canceled or postponed, many of the guests were elated to be back on a ship, even though they were not entirely sure what to expect.

“We’ve cruised about 28 times on all different varieties of ship, but with this crazy virus we didn’t know how this would look and feel, so we wanted to try it out and see if we felt safe,” said Squirrel Simpson, 68, an avid cruiser from Myrtle Beach, S.C., who was sitting with her husband at the pool bar sipping a mimosa.

Her verdict: “This is just incredible, it just feels like we are back in before pandemic times and we are alive again. Interacting with people without masks, eating in restaurants, seeing shows. It’s a dream.”

Yet, Ms. Simpson found the emptiness of the boat surreal and said she missed the buzz of lots of passengers on board.

“Normally, you’d have to come out here at 7 a.m. and you’d be lucky if you could find an empty chair to put your towel on, but now you have so much choice,” she said, pointing at the empty rows of deck chairs around the pool area.

Michelle Lewis, 56, and Chad Curtis, 34, a couple from Orange County in California, sat smiling at one another as they celebrated the first night of their honeymoon at the ship’s upscale Tuscan Grill restaurant.

They winced at the suggestion that they were guinea pigs testing out a series of health and safety protocols.

“I don’t feel like a guinea pig, I feel like a pioneer,” Ms. Lewis said, laughing.

“There might be issues that pop up on the way and I think you have to be prepared for things not going perfectly. But look at us,” she said, gesturing at the ocean in the background. “We are in the middle of the Caribbean Sea on a luxury cruise not wearing masks with wonderful people and crew. It feels fantastic.”

The couple is considering taking a back-to-back cruise with the same itinerary, departing from St. Maarten on June 19.

“Just the idea of not getting straight back on a plane and spending time in a Covid-free bubble is pretty appealing,” Mr. Curtis said.

Usually when a cruise ships makes a port stop, guests can participate in excursions organized by the cruise company or are free to explore the destination independently for an allotted time.

Coronavirus restrictions in Barbados, the first port of call, meant that passengers were only allowed to participate in “bubble excursions” designed to limit interactions with the local population.

There were several options, including tours of the island and its white sand beaches, but the most popular excursion was a catamaran voyage that involved swimming with sea turtles.

Masks were required when passengers disembarked from the ship to take a bus to the catamaran. The catamaran moored not far from shore to allow passengers to swim, but they were repeatedly told not to swim to the beach.

“I would not usually choose to take a shore excursion, and it feels strange to be restricted,” said Harvey Freid, a guest from Miami. “I like to get off and visit local restaurants, try the food, meet local people and check out the casino. But what can you do? This isn’t so bad,” he said.

In the second port of call, Aruba, guests were free to travel by themselves and many leapt at the opportunity.

“It’s really cool to arrive in a new place by cruise ship and get off again and walk around like we used to,” said Marni Turner, 52, a longtime cruiser from Florida. “But it’s weird to have to put on the mask again and worry about Covid. It feels much safer and comfortable on board.”

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