Mariner's not open, yet.... BUT looks like it could be soon. The hotel they're building next to it is almost done and Mariner will probably reopen with the hotel.
Capt. Jacks's on Thomas Drive is another Seafood Buffet you might try.
If you're really wanting a great seafood meal that will leave you stuffed and happy, try Boon Docks Restaurant on Hwy 79. It's not a buffet, but the seafood is premium and the portions are large! Plus they let you mix and match. Go early to avoid a long wait.