Sneaking would not be the word I would use. We just take it on. Carnival does allow 1 bottle of wine per person I think. Check that out with your PVP before you go. But I just make sure I purchase liquor in plastic bottles, put them in two zip lock bags, just to make sure, & put it in the middle of my luggage. Not your carry on. I have seen several people loose their loot with booze in the carry on. I have taken wine & hard liquor this way.
It is pricey, but you can buy bottles directly from Carnival's Bon Voyage Department pre-cruise and have them delivered to your room. They have Rum, Vodka, etc. This isn't list on Carnival's website it's one of those cruising tips. Once you get on board any booze you buy will be held until after the cruise.
__________________ One part age; three parts liquor!
Freedom of the Seas 2012
Carnival Splendor 2010
Carnival Freedom 2008
Carnival Elation 2007
Celebrity Infinity 2006
Carnival Ecstasy 2005
Carnival Paradise 2004
Star Princess 2002
Viking Serenade 1994
Princess will allow a reasonable amount of wine in your suitcases as will H.A.L.
Norwegian CL is much more punitive. They will seize your wine and return it to you at cruise end. Carnival allows one bottle p.p.
Costso sells "Tefft" Cabernet/Merlot, which is an excellent choice for a box wine. Usually box wines a pretty awful. Tefft is an excellent smaller vineyard in Western Washington State and I have never had an unacceptable wine from the vintner. Each box is 4 liters or 5.3 bottles
Box wines are a bit more difficult and much less likely to be discovered by x-ray machines. Mumm's the word!