This is a very reasonable thing to do. It's still at the cruise line's discretion and it may be difficult to get them to say yes since all luggage, checked or carryon, is x-rayed and they have a process for impounding banned items that would have to be circumvented during a very busy time for all crew on the ship.If I were going on a cruise like that I think I'd contact the cruise line in advance. I'd explain that I want to use it at the destination, not on the ship, and offer to let them impound it until the ship reaches port. If you could get agreement in writing, you'd just have to show the response at boarding and probably see someone like the purser to hand it over. Worst case, they still say no, but at least you tried.