Crystal Cruises is simplifying its evening dress code and abandoning formal nights in favour of "black-tie optional" evenings. From 21 December on Crystal Serenity and Crystal Symphony, the "resort casual" and "elegant casual" classifications are replaced by "Crystal casual" - requiring ladies to wear dresses, skirts, dressy trousers, and blouses or jumpers; gentlemen may choose from dress shirts and sport coats (no tie required), open-collar or collared polo shirt and dress trousers/smart trousers.
As the name suggests, "black tie optional allows gentlemen to wear dark suits (with ties) if they prefer not to bring a tuxedo or dinner jacket. Woman will still dress up in formal cocktail or evening dress and separates.
Casual wear is acceptable at any other time of day - although on Crystal that rarely stretches to football shirts and torn jeans.
Adventure Cruising blog