You will see anything from tux & gowns to suits and fancy dresses to (ie my husband) slacks, sport coat and tie and (ie me) simple black dress. I've also see dress kilts and uniforms. Even on HAL, formal "ain't what it used to be". But, I've NOT seen anyone in the dining room that wasn't appropriately attired. HAL is more "low key", but the service is impeccable, the decor and fresh flowers everywhere are wonderful and crew and staff so helpful and attentive. HAL is our preferred line - we'll be doing our 5th sailing with them in February.