Most cruises offer a variety of activities which will require both formal and casual attire. For a formal dinner, such as a Captain's Dinner, pack a formal gown or a suit. Because most cruise ships have dance clubs, casinos and live shows, pack one or two outfits for these, such as a cocktail dress, or for men, a couple of nice pairs of slacks and a few shirts.
Pack a few casual outfits for mornings and afternoons, such as jeans, shorts, or skirts with light blouses and a light jacket or sweater. Pack an outfit to wear to the pool; a swimsuit, cover up, hat and sandals will be ideal. Travel experts at Travels.com recommend packing "light, 'mix and match' clothing that can dress up a casual outfit, especially during the evening hours, dining in the formal dining room or attending special events." They also point out that t-shirts and shorts should not be worn after 6 p.m. in main dining room areas.
When you arrive in Mexico, wear comfortable shoes and lightweight clothing. You will likely be walking most of the day and into the evening, so a sun-protecting hat is also an ideal accessory. Do not wear expensive or flashy jewelry. Bring a light bag in which to carry your camera and any souvenirs that you purchase in Mexico.