Sexual activity among cruise-ship workers is common, but according to Aida Carvahlo — a former human-resources manager for MSC Cruises, Viking Cruises, and Holland America Line — sexual relationships with passengers are forbidden.

If an employee is caught having a sexual relationship with a passenger, he or she is likely to get fired, Carvahlo said.

"We are not allowed to have any type of intimate contact with the guests. We are dismissed for that," she said.

The same is not true of sex with other employees.

"There's a lot of sex on cruise ships," said a former casino manager for Holland America Line.

Cruise ships have intense hookup cultures

Some current and former cruise-ship workers compared the hookup culture as being similar to, or even exceeding, that of a college dorm. And, like college, sexual activity is fueled by frequent alcohol consumption. Sex among employees is so pervasive that former Carnival Cruise Line waiter and art auctioneer Brian David Bruns said a co-worker was surprised when Bruns had not hooked up with one of his colleagues during his first night on a ship.

But the permissive sexual culture on cruise ships can also lead to aggressive or inappropriate behavior. A former Royal Caribbean Cruises employee who now works for Carnival said one of her managers on Royal Caribbean would make comments about her sexual orientation and criticize her for never changing her hairstyle.

Royal Caribbean did not respond to a request for comment.

Read more: A lawyer who works with cruise passengers reveals the one thing you need to know before getting on a cruise ship

Another current Carnival employee said at one point, she was dating a man whose contract was close to ending. Male co-workers would remind her of her boyfriend's imminent departure, and, as soon as he left, made advances under the guise of comforting her.

Relationships move faster than on land

Romantic relationships among employees develop and end much faster than on land, which, along with frequent turnover, can make long-term relationships difficult.

"One month on a ship is maybe like two years on land, because you spend so much time with these people," said Taylor Sokol, a former cruise director for Holland America.

But the close proximity between employees can make it difficult to maintain a healthy amount of space from a romantic partner, Sokol said.

"It's kind of hard to give someone their space when you live maybe 10 feet away from them."

Chad Stone, a former production manager for Seabourn Cruise Line, said the dating scene on cruise ships was part of the reason he stopped working on them. At one point, he got engaged to a co-worker, but ended the engagement a month later after he learned his fiancee had cheated on him during a break between contracts.

Long-term relationships are difficult

The cruise ship lifestyle also makes the prospect of raising children a challenge, as cruise ship workers sign contracts that keep them on board for months at a time. Nina Beader, a former youth staff employee for Carnival, said she decided to stop working on cruise ships in part because she wanted to one day have a family and feared that a cruise ship job would prevent her from spending enough time with her children.

"I did not want to end up being 40 and not having a family," she said.

A Royal Caribbean employee who has spent two decades working on cruise ships expressed ambivalence about the unusual nature of on-board romance. He is considering ending his time on cruise ships in part because they aren't conducive to long-term relationships, but he has also noticed that friends who are in conventional relationships do not appear to be satisfied with them.

"I look at my friends all over the world that have relationships that would be considered normal, and I don't find a whole lot of them too happy," he said. "I'm still pretty happy with my single lifestyle and not having to answer to anybody. I'm okay with that for now."

Have you worked on a cruise ship? Do you have a story to share? Email this reporter at mmatousek@businessinsider.com.