THEY SAT on the beach in a nest of chairs, towels, bulging carryalls and an umbrella. He wore sneakers and socks -- which almost says it all -- and scowled at the incoming waves while his plump, cheery wife rummaged in a large Styrofoam cooler.

Ultimately she managed two stubby glasses full of a fruity looking drink, and a cheese straw apiece.

"There's and in mine," he whined through a mouthful of crust.

"How could there be? I just opened the box."

"It crunches between my back teeth. Why can't we have a drink in the apartment?"

"Because we're at the shore."

By now all experienced beach sitters had collected their trappings and moved out of earshot. Not minding sand is one of the rules. Also, with an opening like thaqt, you knew they'd go on and on. The size of her cooler promised an endless sand-endangered lunch.

Beach eating is one of the more revealing summer activities, telling at a glance where class is and class is not. In this case, class does not mean a peeled peach in a glass of champagne, but surviving a full day in the sun on more than beer and fat pretzels. Like all elements of style, it involves some wit and sensibility.

One casual and energetic woman prepares finger-food picnics as an art form, a colorful array of edibles tucked into clear plastic bags to be set out on the top of the cooler.

When packing for her beach kitchen, she includes all the seasonings she likes the best -- cracked pepper, dill weed, Szechuan pepper and salt dip, sesame oil, raspberry vinegar and whatever.

Day-to-day meals are cooked with the beach picnic in mind. A little extra steak might be charcoal broiled for dinner, and I remember once too much skewered lamb and marinated vegetables that appeared for lunch, all with a delicious charry taste.

Delicatessen wrapplings. A thick slice of smoked thuringer cut into sticks and a thin slice of swiss cheese wrapped around each. Pork roll around a sour pickle spear. Ham around a stick of hot pepper cheese. Genoa salami or prosciutto around bread sticks.

Small pita breads stuffed with saled: sliced radish lavishly dressed with seasoned yogurt . . . sweet onion thinly sliced and dusted with salt, pepper and thyme . . . sliced cucumber with sesame oil and vinegar.

Small, very ripe tomatoes, havled and layered in a plastic bag with too much cracked pepper on each layer. Dill weed on another day and fresh basil when she could find it.

A bag of stemmed grapes for dessert. Or melon cubes seasoned with grated fresh ginger and sugar. A fresh coconut shelled and cut in chunks.

The main work for this kind of eating took place in the market. Kitchen time was almost nothing.

Another hostess responsible for many luncheons on the sand enjoyed cooking. Because it was her vacaton, she limited the menu to one major dish and let crudites and fresh fruit complete either end.

Her sandwiches were only big ones, a large round loaf of Italian bread sliced horizontally in four or five slices and layered with salami, pepper ham, provolone, pepper salad from a jar, peeled and sliced tomato. It was an entire antipasto arranged on the bread, which was wrapped in plastic wrap, stored in the cooler and sliced in generous wedges.

Composed salads with substantial ingredients were another category of main dish. By planning ahead, she could have enough cold beef to toss with cooked vegetables in a sharp vinaigrette. Cold pork with roast peppers and tomato, or cold chicken salad layered between curried rice and a refreshing raita that moistens all of the ingredients without dressing them heavily.

She was the kind of enthusiastic Chinese cook who took a wok to the beach. Leftovers made marvelous picnic food, and sometimes she prepared a stir-fry dish to top a bowlful of cold noodles.

Another category was a two-crust savory pie to be served at room temperature, its custard base ready to receive 3 cups of any tasty combination, not only vegetables, but meat, fish, hard-cooked eggs. In a pinch, uncooked pastry rounds from the supermarket freezer enclosed them. VEGETABLE PIE (5 or 6 servings) 1 small eggplant, about 3/4 pound, peeled and cut on 1/2-inch cubes 1 large onion, chopped 1 green pepper, seeded and cut in 1/2-inch cubes 1 clove garlic, minced 1/4 cup olive oil 2 medium tomatoes, peeled, seeded and chopped 1 cup frozen green peas or finely chopped zucchini 1/2 cup chopped roasted pepper or pimiento Salt and pepper 1 cup grated cheese, swiss, parmesan or a combination 1/2 cup light cream 6 large eggs, slightly beaten Pastry for a 2-crust pie

Saute eggplant, onion, green pepper and garlic in olive oil in a large skiller until the vegetables are soft and begin to brown. Add chopped tomato, peas or zucchini and continue to cook for 5 minutes. Stir in roasted pepper and set mixture aside to come to room temperature. Add cheese, cream, and eggs to cooled vegetables and stir to distribute the ingredients evenly. Season with salt and pepper. Fit 9-inch pie pan with the bottom crust and fill with the vegetable custard. Cut a few vents in the top crust, moisten the rim of the bottom crust and top the pie, pressing the edges firmly together and finishing decoratively. Bake in a preheated 350-degree oven for 1 hour, or until crust is golden. Cool to room temperature and serve as a main dish. CHICKEN SALAD WITH CURRIED RICE (6 servings) Rice: 1 1/2 cups raw long-grain rice 1 1/2 teaspoons salt 2 tablespoons peanut oil 1 1/2 teaspoons curry powder 1/2 cup thinly sliced radishes 1 small green pepper, seeded and finely chopped 1/3 cup mango chutney, mangoes finley cut 1 small bunch scallions, thinly sliced Chicken Salad: 3 cups cooked chicken, cut in 1/2-inch cubes 1 1/2 cups chopped celery 2 tablespoons lime juice 1/2 teaspoon grated lemon rind 1/4 cup vegetable oil Salt and pepper 1/2 cup mayonnaise Raita: 1 meduim cucumber 1 small onion, finely chopped 1 ripe tomato, cut in 1/2-inch dice 1/2 teaspoon grated fresh ginger 2 cups unflavored yogurt Garnish: 1/2 cup slivered toasted almonds 1/2 cup shredded coconut, fresh or, if sweetened, rinsed 1/4 cup seedless raisins

This salad will keep covered in teh refrigerator for 24 hours without losing its punch. Steam rice with the amount of water suggested on the box and 1 1/2 teaspoons salt. Heat peanut oil until quite warm and add the curry power. Sprinkle over the rice when it is done and fluff with a fork with a fork. Cool to room temperature and fold in the radishes, green pepper, chutney and scallions. Use as the bottom layer in a salad bowl.

To prepare the chicken salad, combine the chicken, celery, lime juice and lemon rind and vegetable oil. Salt and pepper liberally and toss. Let marinate for 10 minutes. Then fold in the mayonnaise. Make an even layer of the chicken salad over the curried rice.

To prepare the raita, peel the cucumber and cut in half lengthwise. Seed, cut in lengthwise sticks and slice crosswise in 1/4-inch pieces. Combine with onion, tomato and ginger and fold in the yogurt. Arrange in a layer over the chicken salad. Shortly before serving, sprinkle the salad with almonds, coconut and raisins. COLD CHINESE NOODLES WITH CHICKEN IN BLACK BEAN SAUCE (4 servings) 4 large dried black mushrooms 2 chicken breasts, 3/4 pound each, skinned, boned and cut in 1/2-inch cubes 2 tablespoons soy sauce 3 tablespoons dry sherry 1/4 cup chicken broth, homemade or canned 2 tablespoons red wine vinegar 1 teaspoon sugar 1 teaspoon cornstarch 1/2 pound Chinese fresh noodles, or Italian thin spaghetti 1 tablespoon sesame oil 1/4 cup peanut oil 1 small can sliced bamboo shoots 3 tablespoons fermented black beans 2 large cloves garlic, minced 1 tablespoon minced fresh ginger 1/2 cup celery, sliced diagonally 1 small cucumber, peeled, seeded and cut the same size as the celery 2 scallions including the green, shredded

Cover mushrooms with boiling water and set aside for 30 minutes. Squeeze dry, remove the hard stem and cut 1/2-inch squares. In a small bowl, combine the chicken, 1 tablespoon each of soy sauce and sherry and toss. In a small bowl, combine 1 tablespoon soy sauce, 2 tablespoons sherry, chicken broth, vinegar, sugar and cornstarch. Cook noodles or spaghetti in plenty of boiling salted water until al dente, drain, rinse and toss with sesame oil in a serving bowl.

Heat 2 tablespoons of peanut oil in a wok or large skillet, add the chicken, and stir fry just until it is opaque, about 1 minute. Remove and add 2 more tablespoons of peanut oil to the pan and heat. Add mushrooms and bamboo shoots and stir fry for 1 minute. Add the black beans, garlic and ginger and cook 30 seconds. Return chicken to the pan and continue to stir fry for 1 more minute. Mix the soy-sherry sauce to reblend, add and cook for 1 minute.

Pour the chicken dish over the noodles and agitate the noodles just enough to let some of the sauce coat them without tossing in the chicken. Cool to room temperature.

Sprinkle the dish with celery, cucumber and scallion and serve. You can refrigerate this dish up to a day without dramatic flavor loss. Serve in small cool bowls with chopsticks.