Start with shoes. Good walking shoes with firm support are essential when visiting many European countries. Many tour itineraries include islands with steep heights such as the Italian island of Capri and the Greek isle of Santorini. Make sure that your feet are well cushioned if you want to explore the top of the summit of a long dead volcano or walk up ancient footpaths.
Put on a pair of long pants. Both women and men should bring a pair of long pants. Even if you are traveling during the summer nights can get cold at sea. One pair of well-tailored pants enables you to eat dinner onboard or off shore in style,and still remain warm.
Dress formally. Evening attire is essential on European cruises. Even the most casual cruise will have at least one or two fancy dinners, for which you'll want to be well-attired. An appropriate outfit is also essential if you are visiting religious sites. Many churches, such as Saint Mark's in Venice, require men and women to keep their knees covered when you are touring the church. A good suit is the perfect choice for men and women and allows you to easily adhere to local dress codes.
Wear the right swimwear. Many popular European destinations such as the coast of southern France have excellent beaches. Take advantage of this fact with an appropriate item of swimwear. The most southern of the beaches, such as those in the Greek isles allow for swimming nearly all year long. European bathing codes can be more lax than you'll find in America. Expect to see women bathing topless; if you're comfortable, you can wear a bottom only. Men can wear many different types of swimwear including more form fitting items. However, be prepared with more traditional swimwear as some locations may frown on topless women or men in tight suits. Ask a representative from the ship about appropriate swimwear at different beaches.
Use the right accessories. Sunglasses are widely worn in European countries. Put on a stylish pair during the day. Blend in with the Europeans with the purchase of an upscale scarf such as one from a fine European retailer such as Hermes. Keep makeup light and subtle. Formal dressing in many European locations does not involve the use of heavy jewels.