May you carry your own liquor aboard to drink on a cruise? No. Can you? Probably. About two-thirds of the cruise passengers who responded to a poll on the Cruise Critic site said they had smuggled booze on board cruise ships.
Cruise lines would much prefer you to drink their hooch, at a nice markup. They would prefer it so much that they generally will confiscate any alcohol they catch you trying to bring aboard, although they will return it at the end of the cruise.
There are exceptions. Some cruise lines will allow you to bring wine aboard, but will charge a hefty corkage fee if you want to drink it in the dining room. And some luxury cruise lines are all-inclusive, so there’s no percentage in preventing you from bringing your own.
I can tell you this much. I like tequila, which means that if I’m in Mexico I don’t come home without some. Coming back on board ship with my tequila, it’s been hit or miss. I’ve had it confiscated (and returned before disembarkation) and I’ve breezed right through with it.
An enterprising lad of my acquaintance made an astute observation on this topic. He managed to get a nice bottle of reposado tequila aboard a cruise ship and he figured that it got past the x-ray screening because it was not in a conventional bottle shape. (See photo.) He didn’t drink it on board, anyway, because he was buying it for me.
There’s a lot to say on this topic, and there’s a comprehensive article on Cruise Critic that says most of it.