Shrimp taken straight from southern waters and cooked at dockside in a cauldron of clean seawater and seasoned with spices are an unforgettable delicacy.

Even without the ambiance, shrimp remain our most popular shellfish, known and relished throughout the world. There are hundreds of species, in both salt and fresh water. Most varieties look something like a clawless lobster, and generally range in size from miniscule (requiring hundreds to make a pound) to over 1/4 pound each.

Giant varieties, such as tiger prawns, come from Panamanian and Indian waters; foot-long royal reds are brought up from 1800 feet deep in Flordia's Gulf Stream. Some of the tiniest shrimp are netted off the coast of Greenland. One of the most startling shrimp is the giant macrobrachium, a fresh-water variety that can grow up to 30 inches from tip to tip. This long-legged, odd-looking fellow not only tastes like lobster but can act like one -- it has a claw with terrific pinching power (most shrimp are clawless).

Shrimp are common to nearly all coastal waters, though our main Atlantic shrimping area extends from North Carolina to Florida and the Gulf of Mexico. In the United States, over 370 million pounds of shrimp are marketed each year, and we import at least 200 million pounds more. Marine biologists are working on methods of shrimp farming, but for the most part, we reap the natural harvest of the sea.

The terms shrimp and prawns are often used interchangeably. Correctly, however, prawn should refer to fresh-water varieties, and shrimp to saltwater varieties. It is unlikely that this muddle will ever be cleared up -- in the U.S. and England, prawn is often used to designate large shrimp, and in India, they're all called prawns. Call them what you will, they're popular in every cuisine from Danish to South African.

The best shrimp are those you scoop from the water yourself. Next best are those bought at dockside when the trawlers come in with their catch. But most of us buy shrimp in the markets. When buying fresh shrimp, be sure they are firm and smell fresh, with a tang of the sea, but no unpleasant odor. One bad shrimp will spoil the lot, so be finicky when buying fresh shrimp. Most shrimp are frozen or heavily iced and then shipped to market. Improved methods of packing and handling put shrimp in our markets all year, albeit at sometimes outrageous prices. They are sold by size, or "count" per pound.

There are about seven marketable varieties here, and only a dedicated shrimp-shucker would care to sort them out. Generally speaking, fresh shrimp are grayish-green, pinkish or brown--and all delicious. Here is a rule of thumb guideline for count-per-pound: 10 to 15 per pound: jumbo 16 to 20 per pound: extra large 21 to 30 per pound: large 31 to 40 per pound: medium over 40: small

These are general terms, not exact measures. Other than fresh, shrimp are sold frozen, breaded, uncooked and cooked, canned, smoked, dried, pickled, in paste form and in combination with other food.

A couple of questions always arise concerning fresh shrimp: why do some have a high iodine content, and how do you clean shrimp?

Iodine content in shrimp is in direct proportion to the saltiness of its environment. In waters of low salinity, iodine content is low, and in areas of high salinity, the iodine content of the shrimp will be high. Shrimp from deep ocean waters for example, tend to have high iodine content, and prawns from fresh water will have little, if any.

As for cleaning, most shrimp are marketed with heads removed. However, if you net them yourself, or buy them whole, it is simple to snip the papery head off. Shrimp may be shucked raw or cooked, as you wish. After shucking (shelling) all that remains is to remove the thin black line along the back. This is mostly an esthetic exercise, as it is harmless. Many cooks take the trouble to remove the line from large shrimp, and skip it with smaller ones. If the shell is to be left on, remove the line by cutting through the shell on the back of the shrimp. There is a deveining tool available, but a sharp small paring knife works fine.

Shrimp take well to every imaginable cooking method: They can be boiled, broiled, baked, steamed, barbecued, pickled, curried, fried and potted. In jambalaya, gumbo, newburg, quiche, soup, chowder and casseroles shrimp are perfectly at home. The one universal tenet is DO NOT OVERCOOK SHRIMP. Overcooked shrimp become shrunken, leathery and tasteless. Correctly cooked, shrimp are plump, tender and delicate. Because it is so easy to overcook shrimp, they should be added to dishes at the last possible minute. For the same reason (to avoid overcooking) defrost frozen shrimp before cooking.

Every cook has a favorite way of cooking shrimp "guaranteed" to turn them out tender and perfectly done. The controversy will continue, surely, but here is one way you might try: cook 2 pounds shelled shrimp in 2 quarts fresh water. Bring the liquid to a boil, add shrimp, cover and simmer shelled, medium shrimp 3 minutes; shrimp in their shells need 5 minutes. Larger shrimp will require a few minutes more. Shrimp will turn a lovely pink when done. MARINATED SHRIMP (20 to 30 servings) 5 pounds shrimp, cleaned and cooked 1 pint olive oil (or 1/2 olive oil, 1/2 vegetable oil) 1 green pepper, chopped 4-ounce jar pimiento, chopped 6 eggs, hard-boiled and chopped (use whites only) 2 whole cloves 1 onion, finely chopped 2 garlic cloves, pressed 1 teaspoon salt 1/4 teaspoon pepper 1 cup chopped parsley 8-ounce jar pickle relish 1 cup vinegar

Place shrimp and all other ingredients in a bowl, refrigerate and marinate 2 to 4 hours. Lift shrimp from liquid to serve. (This will keep in refrigerator several days.) BEAUFORT SHRIMP "PIE" (6 to 8 servings) 1/4 cup chopped green pepper 1/4 cup chopped onion Butter for saute'ing 3 cups shrimp, uncooked 2 cups soft bread crumbs 2 eggs 2 cups milk Salt and pepper 3 strips bacon

Saute' pepper and onion in a little butter until soft. Make layers of shrimp, crumbs, onions and peppers in a 2-quart casserole. Beat eggs, milk, salt and pepper and pour over shrimp. Lay bacon on top and bake at 325 degrees until set and bacon is brown. SHRIMP REMOULADE (6 to 8 servings) 2 pounds shrimp, boiled and cleaned Remoulade: 3 egg yolks, hard-boiled and finely chopped 2 tablespoons dijon-style mustard 2 teaspoons minced onion 2 teaspoons minced parsley 3/4 teaspoon salt 2 small gherkin pickles, chopped Dash hot pepper sauce 1/2 cup olive oil 1/4 cup vinegar 2 tablespoons white wine

Mix egg yolks, mustard, onion, parsley, salt, pickles and hot pepper sauce together thoroughly. Add the oil drop by drop, beating constantly with a fork. Gradually add vinegar and white wine. Mix thoroughly, add shrimp and chill. MOLDED SHRIMP SALAD (12 servings) 24 ounces cream cheese 1 1/2 cans (10 3/4 ounce size) cream of tomato soup 3 envelopes unflavored gelatin, softened in 1/2 cup cold water 1 1/2 cups chopped onion 1 1/2 cups chopped green pepper 1 pound cooked shrimp Salt and pepper to taste 3 cups mayonnaise Horseradish to taste

In a large saucepan, stir together first three ingredients over low heat until gelatin is dissolved and mixture is thick and creamy. Remove from heat. Add remaining ingredients. Mix well. Pour into 4- to 5-quart mold and chill until firm (about 3 hours). Unmold and serve with mayonnaise mixed with a bit of horseradish. From "The Pantry Shelf" POTTED SHRIMP (4 servings) 6 tablespoons clarified butter, plus more as needed 1/8 teaspoon mace 1/4 teaspoon nutmeg Dash of cayenne 1/2 pound boiled shrimp, coarsely chopped

Heat clarified butter in skillet. Add seasonings and shrimp. Heat gently together for 5 minutes. Pour into small pots or custard cups and press down. Add more melted clarified butter to cover shrimp. Cool, cover and refrigerate until clarified butter is firm. To serve, unmold on lettuce leaves. CURRIED SHRIMP IN AVOCADO HALVES (4 to 6 servings) 2 or 3 avocados 2 tablespoons lemon juice 1 tablespoon butter 1 teaspoon curry powder 1 teaspoon salt 1/3 cup onion, chopped 1 large tomato (1 cup), chopped 1 pound shrimp, cooked and cleaned 1 cup sour cream

Halve and peel avocados. Brush each half with lemon juice and place in shallow baking dish. Heat for 10 minutes in a 300-degree oven. In a saucepan, combine butter, curry and salt. Stir in onion and tomato. Cook until onion is tender. Add the shrimp and heat about 3 minutes. Blend in sour cream. Heat but do not boil. Spoon mixture into warm avocado halves and serve at once. SCAMPI (2 to 4 servings) 1/2 cup butter 2 teaspoons worcestershire sauce 1/4 cup sherry 1 garlic clove, finely chopped 2 tablespoons lemon juice 1 tablespoon sugar 1/4 cup parsely, minced 1 pound raw shrimp, shelled and deveined Parmesan cheese and rice

Melt butter in a shallow pan over low heat. Add worcestershire sauce, sherry, garlic, lemon juice and sugar. Mix well. Arrange shrimp in a single layer in a baking dish. Spoon sauce over shrimp and broil at low heat for 8 minutes. Remove from broiler and let stand 15 to 20 minutes. Sprinkle with parsley and broil at high heat for 3 minutes. Spoon over hot rice, sprinkle with parmesan cheese, and serve. Garnish with parsley. SHRIMP CREOLE (6 servings) 2 medium onions, chopped 9 garlic cloves, finely chopped 6 stalks celery, chopped 2 medium green peppers, chopped 4 tablespoons butter or bacon fat 8-ounce can tomato sauce 4 cups whole tomatoes (preferably Italian) 1 lemon, thinly sliced 1 cup dry white wine 1/2 teaspoon cracked red pepper 1/2 teaspoon black pepper 1 teaspoon sugar 2 bay leaves, crushed 1 1/2 teaspoons dried basil 1 1/2 pounds uncooked, cleaned shrimp 1/4 cup dry sherry 1 teaspoon worcestershire sauce

In a heavy skillet, saute' onions, garlic, celery and green peppers in butter (or bacon fat) until wilted and transparent. Add tomato sauce, whole tomatoes, lemon, wine, red pepper, black pepper, sugar, bay leaves and basil and simmer 35 to 40 minutes over low heat. (Keep heat low to prevent sticking.) Add shrimp and cook until shrimp are done -- about 5 minutes. Add sherry and worcestershire sauce. Simmer gently for 15 minutes to develop flavor. Serve with 1 cup hot rice per person. BREADED SHRIMP (6 servings) 1 1/2 pounds shrimp 2 eggs, beaten 1 teaspoon salt 1/2 cup flour 1/2 cup dry bread crumbs

Peel shrimp, leaving the last section of the shell on if desired. Cut almost through lengthwise and remove veins. Wash. Combine egg and salt. Dip each shrimp in egg, and roll in flour-and-crumb mixture. Fry in a basket in deep fat, 350 degrees, for 2 to 3 minutes, or until golden brown. Drain on absorbent paper. Serve plain or with a sauce, such as tartar, gribiche, creamy dill or sour cream dressing.