There's 2 buffets at Rio, there's the Seafood, then there's this one Carnival World which doesn't have much seafood, except for shrimp cocktail, and really bad crab legs (tiny, slim, little meat, very very hard to get the meat out), not that fresh.
There's huge selection, but the food wasn't that great, I'd call it mediocre.
The prime rib was mediocre as expected for a buffet. The mashed sweet potatoes was good. Most of the food was kind of too salty I thought.
I probably wouldn't come here again knowing there better options elsewhere.