No, there aren't any raw oysters on the half shell in the buffet or dining room. But, if you order the Asparagus Veloutee on the first night, you will receive asparagus soup with a small raw oyster (no shell) in it, if that counts.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08
They do however have fried oysters on the Valor (and I believe the Legend) - right above the main lido deck buffet line on deck 10. They serve awesome fish & chips and fried oysters. I guess if you can't get them raw this would be the next best thing!