I rarely post on Chowhound, but I found such a small amount of recent information about any restaurants in the Destin/Ft. Walton beach areas before I went there, I wanted to write about at least one place I went to that I heartily endorse if what you're looking for is authentic, local seafood. It is Stewby's Seafood Shanty, located at 427 Racetrack Road Northwest, Ft. Walton Beach, FL 32547, about 12 miles from Destin.
It is a no-frills establishment (order at the window, eat at a picnic table) that only serves fresh local fare, and no matter what method they cook it, it's simply fantastic!!! We enjoyed grilled Mahi-Mahi and shrimp, fried snapper, fried oysters, hushpuppies, collards, and cheese grits. They advertise that they are not a fast-food restaurant, but everything comes out fast, hot, crispy and flavorful. Oh yes, and an AMAZING gumbo, deep and filling, like I haven't had in ages.
Skip the fancy, neon monstrosities on the beach and hit this place. You won't regret it!!!!