I have gained 9 pounds on a 5 day cruise. My sister and I both worked out as well but every time you lookd up, we were eating. I always anticipate weight gain and bring workout clothes and am fierce about working out daily to try to keep it to a minimum.
This last cruise, I gained about 3 pounds on a 7 day cruise but took it off the next week when I returned home.
Its so much fun, I wouldnt have it any other way!