There was a mixture on our last med cruise, but I would say the underdressed people were in the minority. On a 7 night, there will generally be one formal night and one semi-formal night. Formal night is tux and ankle length dress for the ladies. Semi-formal night is cocktail for the ladies and suit/tie for the boys. We met a couple last year who didn’t make the effort and thought it wouldn’t matter that they hadn’t put on anything fancy, and it turned out they felt really awkward going out to dinner in very casual clothes and sitting at a table with people who had made an effort and were wearing a tux and long dress. It is all down to the individual, but it will say on the navigator what the dress code is and the staff will be dressing accordingly too. Without fail on 7+ day DCL cruises, the formal night is on the first sea day, so no-one has been running around ports all day and have no time to get ready. Come on people, we are on a beautiful ship sailing round the med, let’s all look fabulous !!!!!