Check the cruise line web site for size restrictions for carry-on luggage. Carnival is 16" x 24" x unlimited, plus you can take a small cooler no larger than 12" x 12" x 12". I also asked about bringing bottled water and they said yes but not a huge amount (suggested a 6 pack), but emphasized that the water needed to be sealed. I guess that means if you bring an open water bottle you'll have to throw it away.