Sailed with Costa through the Carabbean in Jan and a good number of men were wearing dinner jackets. Some also in suits so i would say an effort was made by many. even the men who did not wear a jacket had a shirt and tie on. I personally love to see a man in a dinner suit (very James Bond)and have just convinced my hubby to buy one (after 5 cruises) which we are taking with us next week on our cruise through the Panama! Don't forget the Costa is an italian cruise line and the italians always love to dress up especially the women, some outfits were outstanding. I would say the dress code was "very smart" a little more effort was made.......We really enjoyed with Costa so much so we have booked with them for Canada and New England next year. You will enjoy!!!!
We cruised on the Mediteranea in January. Two of the seven nights were formal with some guests wearing black tie / kilts. Other guests were in lounge suits and a few in resort wear.