Jeans are not suggested on most ships, and some will clearly state so in the material. Having sailed Celebrity in Europe last year, and again this summer, you would feel pretty uncomfortable in them. If you're going to Alaska, dress code is considerably "looser" all around. Hope this helps a little. Also, in Europe, if you're doing churches, palaces, museums, etc., they also have far stricter dress codes. Your brochures and shore excursion books should be able to tell you what is proper, or check with your travel agent.