For semi formal attire, the man is requested to wear a jacket with tie, thus creating a little more formal atmosphere. Ladies usually wear nice pants suits or dresses (like Sunday dress of day's gone bye) And you will see lots of in betweens. For casual, jumpsuits, pants, skirts, sun dresses (for tropical itinerary), casual pants suits, etc. Shorts, jeans and t-shirts are not appropriate evening dress. Most people also remain in the requested attire for the evening as well. Have a great cruise. Planning is half the fun.