The following is purely for entertainment purposes, I don't expect anyone to try any of these things, I am just sharing this purely hypothetical info for entertainment purposes, since someone asked.
I dont know how thorough they are on cruise ships, but I imagine they are much more concerned about people bringing stuff back on to the ships from the ports of call, rather than when leaving the USA or Canada, etc. So, here are a few methods that range from the slightly inconspicuous to straight jailhouse methods.
The first method is simple. Take edibles. These usually pack a nice punch if made correctly, and no one is going to question a tupperware full of cookies or brownies. Just say they're a snack for the beginning of the trip.
Second method is a little more meticulous. Pre-roll a few joints, empty a cigarette pack of a few cigarettes, and replace with joints. You can even cut off the filters of the cigarettes, make the joints a little shorter (orget 100s for example) and place the filters on top of the joints, hiding them. You probably want to avoid placing anything in checked luggage, because, honestly, you dont really want the stuff leaving you. If its in your pocket in a pack of smokes, you know where it is at at all times. Who knows if they have a random drug dog sniffing ALL the luggage once its in the hold.
Now, we are movin on to the jailhouse methods, of which I only know 2-3 that would work. The first is for the not so adventurous. Tape a bag of smoke to the inside of your thigh. Like I said, unless you get strip searched or a dog sniffs you, you will know where the stuff is at, and it will be close by if you need to ditch it. They do search you in jail... Strip search in fact, with a little bit of cheek spreading and coughing, which brings us to our next methods.
The last couple methods involve some committment. The second a little more than the first. The first method is called "Cheeking". You take a bag of weed, and place it between your butt cheeks. Sounds funny, but really, who's gonna look down the crack of your *** for drugs? Well, cops will, you can be sure of that. If you think the cruise ship people are going to be that thorough, you could always pack the weed as tight as you can, place in saran wrap, and try to make it as cylinderical as possible, and, you guessed it, stick it up your butt. I know, I know, it sounds gross, and I have never done it, but I know it works (its how most drugs are brought into jail, if you've ever wondered. People bring stuff with them when they turn themselves in. Your colon is about 8 inches long, so, you can place a cylinderical package about 2-3 inches long and about the diameter of a dime or nickel, and make sure its in there at least 1 knuckle deep. (I know it probably sounds like total disconfort, but, just think, if you were a heroin addict and you were going to jail for a month or two, you would definitly stick some drugs up your butt then...). Anyway, Im not condoning anyone breaking the law... You asked for this information, and I just wanted to share and add to this obviously hypothetical conversation, right? *wink wink* *nudge nudge* know what I mean?