Check with the cruise line to find out exactly what the regulations are about bringing alcohol on board. You should also know the repercussions if you get caught smuggling booze onto the ship. These can range from a warning and confiscation of the alcohol to being removed from the ship.
Bring only what you will use. Don't bother smuggling 10 bottles of alcohol on if you are a light drinker. Plan for what you think you will likely consume. Plus, one bottle of vodka might be overlooked, whereas a case of whiskey probably won't.
Buy beverages that look similar to what you are bringing on. If you are bringing vodka, buy a clear soda with a screw-off lid. If you are bringing on Bailey's Irish Cream, try Starbuck's Frappacino bottles.
Transfer the alcohol to the non-alcoholic bottles. Know that some screw lids will leak when repackaged so you might consider storing them in gallon-sized plastic bags in your luggage, just in case. A suitcase reeking of booze will no doubt cause suspicion.
Put it in your checked baggage. When you get to the cruise terminal, you will be checking your large bags. Make sure that the alcohol is in them. You can bring a small bottle with you on the boat for when you set sail, but be aware it's more likely to get checked and confiscated.
