I have been on more the 15 cruises and have taken "it" with me on all of them!
I was more worried about the airport (to get to the cruise) if you stow it on your person wrapped tightly and placed so it wont slip or shift you should be fine. I have a "clean" pack that I prepare a few days before the trip
Clean the outside of your "package" with hand sanitizer then stow it away.
A small amount (less then 7 grams) should not be a problem if by some crazy fluke you are asked to secondary search (airport)
If you place it in your luggage the dogs will seek it out!
bomb dogs will find drugs too!
Use care smoking in hallways or public places (not recommend)
Cruise ships have cameras over every inch of a ship
Smoking in your head (bathroom) on the shitter will work find. The air system will suck it out to the top of the ship and no one will know the better
One word of advice is keep your weed hidden and tightly wrapped even in your room.
Brush your teeth and wash your hands after your session
leave no visible signs of lighters or matches or ashes left in your room or head
Your cabin boy WILL report or confiscate any signs of this or leave you a note telling you smoking in the rooms is prohibited (happened once with my incense)
I know it sounds like a lot but cruise ship have their own rules and can detain you (in their holding rooms) for the duration of your cruise
It has never happened to me but I've heard of it!
Use your head, smoke your weed and you can have a great cruise!
I went to Alaska last month and had a outside veranda and smoked my blunts as we sipped coffee and watched the icebergs floating by !
Have fun!