With all the dignity and hushed importance of the state room of a luxury ocean liner, Oceana is as nautical as it gets on land. Chef Cornelius Gallagher quickly leapt right into the ranks of New York's best seafood chefs, and he is not without distinctive whimsy and even theatricality. Thus, blue marlin -- not often encountered in these parts -- is served rare with phyllo hugging it and accented with Swiss chard and glazed peaches. Halibut is brushed with melted espresso butter and plated with corn, pine nuts, and mustard greens in a pool of hot basil corn milk. Finish with a lime tarte tatin with Gewürtztraminer gelée cubes. Gallagher's is some of New York's most imaginative cookery -- seafood or otherwise. Subway: 6, 7 to 51st St.