Each cruise line has its own dress code, however generally speaking:
Expedition is casual
River cruises are casual during the day and smart casual in the evening
Ocean cruises tend to be casual during the day, smart casual at night with the occasional ‘dressy’ or even Black Tie evening, especially if your cruise is 10 nights or longer.
For more details, each cruise line clarifies this in their confirmation and ticket documents.
Let us know if the formality of dress code is important to you and we will suggest the most appropriate cruise line.