Carnival Cruise Line warns its passengers about onboard behavior

At their best, cruise ships bring people together. 

Everyone on board wants to have a good time, and in most cases that works even with thousands of people crammed together in a (relatively) small space. 

Not everyone, however, plays by basic courtesy rules. Sometimes, cruise passengers have to deal with everything from unruly, unsupervised children to rude adults, and the occasional drunken idiot.

Related: Carnival Cruise Line pushes back on key drink package complaint

This delicate balance of thousands of people getting along and having fun in a confined space can be ruined by a very small number of idiots. One belligerent drunk who starts a fight or a person smoking in a nonsmoking area can create a situation that escalates quickly.

Most cruisers have seen the videos of fights that have occasionally broken out on cruise-ship decks or other situations where things have gotten out of hand. 

Now, during Spring Break season, Carnival Cruise Line (CCL) has proactively sent an advisory to passengers booked on its cruise ships.

Basically, it's a preemptive warning and guide telling passengers how they should act on board. It's also a reminder of the cruise line's basic rules and an effort to reinforce what's allowed and not allowed on board.

Carnival shares key rules with passengers

Spring Break is not unique to Carnival. Royal Caribbean, MSC Cruises, and Norwegian Cruise Line will all have younger-than-usual passenger loads for much of March. 

Carnival, however, does have a reputation as being the party cruise line. The company is aware of this, so it's trying to get ahead of any potential problems with an email it sent to all passengers sailing during Spring Break.

 "We want you to have a fun vacation but please remember a cruise ship is a shared space," the cruise line wrote. "Our Carnival Values underscore that all guests should feel welcome and included, and that everyone demonstrates care and respect towards each other. 

"Our experience has taught us that everyone has a better time when children are supervised, noise in the hallways is kept to a minimum, guests follow queues, and that a spirit of community and neighborliness is shown by all." 

Carnival requires all guests to acknowledge its Code of Conduct before they board one of their ships.

"Please become familiar with these guidelines, and if you are sailing as a group or family, please make sure you have a conversation so that everyone understands how they can support the shipboard leaders in creating a fun and safe environment," Carnival added.

Carnival reminds passengers what's allowed 

A cruise ship is not the same as a land-based hotel, partly because the ship sails to multiple countries where rules can vary. 

Carnival, for the most part, follows U.S. law, meaning that its ships sailing from America offer alcoholic beverages only to those 21 and older. That holds for passengers on board even if the ship stops at a place where the drinking age is 18.

Carnival, and all cruise lines, also have rules about what passengers can bring onboard.

"No hard liquor or beer may be brought on board. Guests 21 years of age and older may bring one bottle (750 ml) of wine or champagne, per person, in their carry-on luggage when embarking for their cruise," Carnival detailed.

You can also bring 12 cans or plastic bottles — but no glass — of water or soda per cabin in your carry-on bag. Beer and similar beverages are not allowed at all.

The cruise line also outlaws marijuana and cannabis even when it's from a state where consumption is legal or the person has a medical card.

"Carnival recognizes that some states in the U.S. and destinations have legalized the use of recreational and/or medicinal marijuana, including its derivatives in products like chewables," the cruise line added. 

"However, cruise lines are required to follow U.S. federal law, which strictly prohibits possession and use of marijuana, including cannabis and its derivatives, and other illegal substances. Consequently, these items are not allowed on board."