I think every cruise line has different procedures as far as how thoroughly they check for alcohol. Ive had some friends that have bought one of the enormous listerine bottles and then drilled out the bottom (to keep the seal on top) filled it with vodka + blue dye and then seal the bottom with wax and voilą you have brought nearly undetectable alcohol.
Also the only way to get legit CCs anywhere in the world is to look for the Habanos sign in the window. Im sure Im preaching to the choir but Habanos is the only legal exporter of CCs and any store that gets them must display the sign.
