ARDENT SEAFOOD epicures will gather in Beaufort, N.C., Thursday afternoon from 2 to 4 o'clock for the annual Strange Seafood Exhibition sponsored annually by the Hampton Mariners Museum. The exhibition demonstrates to the attending enthusiasts that some of the lesser known and more esoteric seafood is indeed palatable.

But just as the first man who ate a raw oyster had to be very hungry or very brave, a certain amount of sangfroid is necessary for sampling the concoctions cooked by volunteers. Do not be misled. The place is thronged every year with those curious and anxious to see what's cooking and what's happening.

What's happening is that North Carolina is having its seafood industry promoted and visitors to the picturesque town are having a whale of a good time and sampling some oddball kettles of fish. And what's cooking may include, as it did last year, everything from Left-hand Whelk Chowder to periwinkle in garlic butter to octopus salad. There will be more than 40 seafood dishes.

Cooks at the exhibition also make it clear that sailing into new culinary waters does not end with the fish but includes marine life such sea purslance, sea kale, glasswort, sea lettuce and sewing thread seaweed.

The exhibition has been so popular that the Hampton Mariners Museum has published a cookbook, "Strange Seafood Recipes," with entries ranging from deep-fried whitebait to batter-fried ray, charcoaled shark steak to marinated tilefish with tomatoes, and even herring roe and eggs. Recipes, by the very nature of the subject, have to be a bit flexible and freewheeling. The assumption is that anyone stout hearted enough to clean and cook an octopus will be able to judge how much butter is needed to saute' it.

Adventurous cooks may order the book from the Hampton Mariners Museum, 120 Turner Street, Beaufort, N.C. 28516. Enclose a check for $6 to the museum. CHARCOALED SHARK STEAK (4 servings) 2 pounds shark filet, cut 1 inch thick Juice of 2 to 3 lemons Melted butter Onions, cut in rings Salt and pepper to taste

Squeeze lemon juice over filets, add water to cover and soak overnight. When ready to cook, drain and pat dry, brush filets with melted butter, dot with onion rings, salt and pepper to taste. Cook over charcoal, about 5 to 7 minutes per inch, being careful not to overcook. DEEP FRIED WHITEBAIT (3 to 4 servings) 2 pounds whitebait (herring or anchovies) 2 cups milk 1 1/2 cups all-purpose flour Oil for deep frying, preferably peanut oil Salt and pepper to taste 4 teaspoons fresh parsley, minced 2 lemons, cut in wedges

Drain fish if necessary, and mince. Soak fish in milk for about 30 minutes. Drain again and coat with flour. Lower into a deep fryer containing very hot oil and turn with slotted spatula until golden brown. Season with salt and pepper, sprinkle with parsley, serve with lemon wedges. BATTER FRIED RAY (2 servings) 1 cup flour 1/2 teaspoon baking powder 2 teaspoons salt 1/4 teaspoon black pepper 1 egg, separated (white beaten) 1/4 cup lukewarm water 1 tablespoon melted fat 1 pound filet of stingray, cut in 1/4-inch-thick, serving-size pieces Oil for deep frying

Sift together flour, baking powder, salt and pepper. Drop in egg yolk, add water and fat and mix well. Fold in beaten egg white. Dry pieces of ray and dip in batter. Fry at 350 degrees in deep fat for 4 to 6 minutes or until golden brown. Drain on paper towels. HERRING ROE AND EGGS (2 to 4 servings) 1 teaspoon cooking oil 1/4 pound fresh herring roe 3 to 4 eggs Salt and pepper to taste

Coat bottom of frying pan with cooking oil at moderately high heat. Drain herring roe and add to pan, breaking up the roe with a fork. Cook for 2 minutes. Stir and separate, leaving spaces where the pan bottom is showing. Crack eggs one at a time into the pan spaces, unscrambled. Allow to set until egg white congeals slightly; then scramble with roe until mixture is dry. Serve with hot grits. MARINATED TILEFISH WITH TOMATOES (4 servings) 2 pounds tilefish filets 2 red onions, sliced thinly Juice of 4 limes Basil and thyme to taste Sliced tomatoes

Place tilefish filets in shallow glass baking dish. Place sliced onions and tomatoes on top of filets. Mix lime juice, basil and thyme and pour over all. Cover dish, refrigerate and let marinate overnight and serve.