Depends, it's up to you. Years ago you saw people really go all out...fancy dresses for ladies and a tux or nice suit for the guys. Lately, not so much. Personally, I don't care to get that dressed up on vacation, but some people do. You're on vacation, so whatever makes you comfortable!!
Carnival Inspiration 09/02, Carnival Sensation 06/07, Carnival Glory 04/09, Carnival Glory 06/10, Carnival Fascination 12/10, Carnival Paradise 11/12