We went on the 4 day cruise this Feb. Dress was casual church style. Women wore mostly skirts or dress capri's and men wore collar shirts and slacks. I saw very few in full suits and no semi formal dresses at all. Actually the only night we saw suits was the night we dined in Triton's. I'd say pack casual and mix in a few nice pieces and you'll be fine. Believe me it is a very relaxed atmosphere.
HAVE FUN