Shorts are not supposed to be worn in the dining room for dinner service. They can be worn at night in the rest of the ship. Polo shirts are fine, and it is something I normally wear with slacks for casual dress dinners.
I have black pinstripe tailored bermudas that are part of an outfit with jewelry and a fancy belt, shoe with heel, etc. I have worn them on a couple cruises to the dining room. No one will stop you when you are that put-together. If you are just wearing shorts or bermudas because you want to skip dressing up you will look and feel out of place in the dining room. If this is an issue for you go to the windjammer and wear what you want. Lots of women wear capris, dressy and sporty. If you don't wear tennis shoes with them they are just fine.
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Laurie
RCCL Nordic Empress 1993
RCCL Nordic Prince 1994
RCCL Explorer 2003, 2005
RCCL Navigator, 2004, 2007
RCCL Mariner 2006
RCCL Liberty 2008
RCCL Adventure 2009 Read and post cruise reviews