ive done this alot! lol
ive been on like 6 cruises, every one i have been on i have got liquor on to the cruise with no problem. besides once, because i had single shot bottles in my pocket, which set off the metal detector, but the security guy surprisingly gave the 2 little bottles back, meanwhile i had a bottle of rum sitting in the water bottle i took off the ship.
so if you want to get liquor on to a cruise ship, buy a water bottle that they sell on the cruise, preferably the large water bottle. be careful, some duty free stores allow you to take the bottle and some do not, if they dont allow you to take the bottle, dont buy it because they will send it to the ship, which you wont get it back till the last night
if you can get one at the duty free and walk away with it, or if you need to find a liquor store, do that, then pour it back into the water bottle and go back to the ship. just make sure you get all clear liquor, or your going to fuck yourself over. if you want something dark, only suggestion i would have is to say you put ice tea in the water bottle. or see if they sell ice tea anywhere so you could do that.
now keep in mind, i have not been on one in about 3 years or so. they may have changed a bit but they never opened my water bottle to see what it smelled like.
its better than paying 5$ a beer on the cruise, or like 7$ for a mixed drink!
word of advice, if you go on the cruise and you get a bottle, and you want to make mixed drinks, buy a pop card before you depart the first night, or when you first walk on the ship.
edit: be careful about bringing a bottle on the cruise when you board for the first time, if you have it in your suite case, they can take it from you, this has happened to a few of our friends that went. some got away with it, some didnt.
also youll be up shits creek for the first night or 2 if you dont stop at a port. youll have to buy beer iirc or liquor but have fun paying the price