But now they are a hotbed of sex and scandal, with 80 per cent of passengers admitting to getting frisky on board and one in five cheating on their partners, The Sun reports.
Here, a former cruise ship worker reveals what life at sea is really like.
Threesomes, orgies and partner-swapping — it’s all going on, while passengers get frisky with each other at every opportunity and even get the crew to join in.
Jane Thomas, 26, from London, worked on board as a singer in the entertainment team.
“Once people get on a ship it’s like getting away from everything. People feel they can get away with anything,” she said.
“They take risks they wouldn’t in the real world. I can only compare it to [British television series] Love Island. You’re in a weird bubble.
“The number of people who use it to cheat is amazing. And they’re so obvious. I remember one guy saying, ‘I bring my girlfriends on here when my wife thinks I’m away for work’.”
Thomas said passengers on the cruise would “tell us everything” — and it seems they saw a lot, too.
“There are lots of swingers too — keys in a bowl, that sort of thing,” she said.
“You would see a woman with her husband, then a different man another night. His hand would be up her skirt. Anything goes when everyone is on board.”
Sex with passengers is a sackable offence but Thomas was constantly propositioned by guests. She always declined.
“They would say, ‘Do you want to come back to my suite later?’ I’d always tell them we’re not allowed,” she said.
“However, my female friend had a threesome with two male guests. She had a boyfriend at home and was so innocent when she arrived. Fast-forward three months and she’s having a threesome. We were shocked.
“Being on the ship completely changed her personality. She just said, ‘I don’t care, I’m not going to see them again’.”
Thomas also revealed one male colleague donned a disguise to avoid being caught by security cameras for a night of passion in a female guest’s cabin.
“He disguised himself wearing different people’s clothes and borrowed a wig from the costume department. It was pretty extreme lengths to go to,” she said.
Sex at sea among the crew is even naughtier, with competitions staged for the most conquests and even a points system broken down by department.
“They have a ranking system and people are ‘worth’ different amounts,” Thomas said.
“If you sleep with someone who worked in the spa, they are higher.”
A male crew member, 28, who wished to remain anonymous, added: “People who work in the spa have higher privileges, so they would be three points, for example.
“Someone who works in hospitality would be two points and a cleaner would be one point.”
Partner-swapping was rife among the crew, the male crew member said. “You might be with someone one week, then someone else the next. There were always little parties happening in the crew areas.
“I once walked into a crew cabin and there were six people in the room. There were two on the bunk bed having sex, two in another bunk bed naked, a person waiting to have sex and one person just sat on their phone. The door was open. Another time,
two guests invited my friend for a threesome. They were a couple in their thirties. He went in their cabin and they just started taking their clothes off.
“Whatever the guests want, the guests get.”
Another former cruise worker, Laura (not her real name), 27, was invited for sex just seconds after boarding ship on her first contract.
“A barman held my hand, welcomed me to the ship and surreptitiously passed me a bit of paper with his cabin number on it,” Laura said.
“It was an invite to meet him later. Suffice to say I didn’t take him up on his offer. That was my first introduction to the below decks shenanigans.
“I later found out when new crew sign on it can be called ‘going fishing’ — more fish in the sea to get their hooks into, that sort of thing.”
Laura, who worked for several years on the entertainment production team after graduating from university, slept with six people on her first six-month contract.
“That isn’t too bad, but that’s considering I’m normally quite reserved,” she said.
The cramped conditions crew share force some to get creative in search of a private spot for sex.
“The backstage area of the theatre was always a keen choice,” Laura said.
“Often there was some sort of bed or sofa and security didn’t tend to prowl through very often. You could always tell who had been having a cheeky one on the floor of their cabin, as the carpets were so rough the girls would have carpet burn on their knees.
“It was a sign they couldn’t fit in the bunk beds — and were lucky enough to have the cabin to themselves.”
With all the bedhopping going on, it is little surprise that some crew ended up with an STI to go with the sun and the sea.
Laura, now married with a young child, said: “I’m ashamed to say I did get an STI. There were always lots of crew at the doctor on board, waiting to have an STI test.”
While cruises can be a great way to meet new people, not everyone is looking for a night of passion.
Adam Coulter, managing editor of Cruise Critic, the world’s largest cruise review and planning site, told The Sun: “Cruising has never been such a hot holiday choice for younger travellers.
“It’s understandable why more millennials are tempted to try a cruise for the first time.
“First of all, there’s more on offer for younger holiday-makers than ever. Cruise lines are bringing what people want on board their ships or taking people to exactly what they want to see.”
The Sun recently reported revellers will be flocking to join the world’s most outrageous sex ship, Couples Cruise’s Naughty Los Angeles.
The four-day trip sets sail from Los Angeles in October and will feature outrageous on-deck action including naked bodypainting, kinky sex toys and 24-hour nudity.
Jane, meanwhile, has returned to life on dry land after finishing her contract in November last year.
“I met my boyfriend on the ship and I needed to know if our relationship would work out or not,” she said.
“Our big dream is to work in the West End or on TV but you can get sucked into ship life. I know people on their seventh contract.
“I needed to live in the real world. It’s too crazy on the waves.”