BAHIA

The sun was low. It was high tide exactly. I was wedged in a crush of exuberant celebrants, standing midway on a long flight of narrow stone steps above a large crescent of white beach. Huge round baskets overflowing with flowers were being hurried past more and more frequently through the mass of bodies around me, borne overhead by strong brown male arms, to a surging ebullient roar. The beach below had become invisible, replaced by a solid mosaic of people spreading out into the water, obscuring the shoreline.

The boats of local fishermen, saveiros, with their sails obliquely furled, jostled each other in the tiny harbor, their crews gesturing excitedly, their bright accent colors a jumbled pattern of horizontal stripes. Children splashed and played around the boats, diving from the rocks that dotted out into the shallow water from the stairs where I stood. Young women, singly and in small groups, were wading out in long organdy dresses, clearly their best, plainly conscious of the honor of representing the fleet, of sitting among the flowers in the heavily laden boats.

And occasionally, a large black woman in voluminous white lace would sway purposefully down the steps, a stately and solemn figure for whom a way was quickly cleared, to take her place regally, almost as a figurehead, in a saveiro. What had begun with great quiet at 6 a.m. had reached a crescendo.

I was witnessing a festival inspired by the strong influence of African culture in Brazil. I was in the city of Bahia, known outside of Brazil as Salvador, (officially Sao Salvador da Bahia de Todes os Santos.) It was founded by the Portuguese in 1549, the first city in Brazil and capital of the colony for over two centuries. A city that has always turned her face to the sea in trade and communication with her seafaring motherland.

Bahia's wealth was built on vast sugar plantations in the state of Bahia and in the adjacent northeast coastal area - plantations worked exclusively by slaves. The city became as well an entrepot of the slave trade. In 1960 three-quarters of the population of the state of Bahia was African or of African origin. The city of Bahia is the most culturally African of all the cities in South America.

Perhaps because of Portugal's long history of subjugation to dark-skinned and sophisticated Arabs, it exhibited less prejudice against racially mixed marriages and a greater flexibility in permitting cultural differences than other nations colonizing the continent. The integrity of the slave family was formally respected by the Portuguese; individual emancipation was possible. Slavery was not the totally closed system it was in other New World colonies.

In Brazil, the African spirit survived slavery. It survived - and it gave to the colony and the country of Brazil a vibrancy seldom paralleled. The mix of that vitality with the austerity and drive of Western European civilization, with all the daring and imagination of 15th- and 16th-century Portugal produced a culture palpably different from any other in the world.

There exists in Brazil a powerful, pervasive optimism. Today is everything and tomorrow will be good. There is the sense, as on the 19th-century American frontier, that everything is possible - but with a simultaneous embracing of life that is wholly Brazilian. Jorge Amado, a Brazilian novelist of major international stature, told me in a recent interview that he thinks ''some religions are based on thought and intellectual theory; in Brazil, religion is life itself.''

There is in the life of Bahia a wonderful naivete, a changing of mood that is spontaneous, of the moment, as wide-ranging as the changing light on the city.

I was walking at noon between a row of improvised restaurant stalls. The sun was blinding white. A middle-aged woman moved slowly on the periphery of the tables, a large aluminum pot of crabs balanced on her head. Small stands sold pressed sugar cane or skewers of meat. Young boys held high long sticks, dangling a rainbow of ribbons, souvenirs to be knotted around the wrists. People milled in the street. And everywhere there was a reaching out, a touching , laughter that included everyone in the vicinity.

By one restaurant, a very dark woman of great bulk sat on a low stool on the ground surrounded by the mounds of her wide white hoop skirt. Her face under a white turban was that of an astute, no-nonsense business woman. Around and in front of her, under a boldly patterned umbrella, was spread an exquisite, almost Orientally designed assemblage of beautiful bits of food. She, like many other women, was selling acaraje, a bean paste deep-fried in palm oil, folded over crushed shrimp with pepper sauce, and eaten sandwich-fashion. Acaraje is synonymous with celebration in Bahia - the aroma blending with that of crushed flowers to create its own version of Proust's madeleine.

Abruptly, down the street, an excited knot of men and boys began to shout and to gesture dramatically. Almost at the same time could be heard the first notes from a berimbau, a colorfully round gourd set upon what looks like a long bow, part stringed instrument and part percussion. Capoeira! Capoeira happening just for the sheer joy of it, unplanned, unannounced, in the middle of this small street. Two black men dressed in shorts flying through the air defying gravity in a kind of magnificent and forceful ballet.

This sport was brought to Brazil with slaves from Angola, and developed in the colony because slaves were forbidden to use their fists or weapons of any kind. Capoeira thus depends on the feet and consists of a range of aerial moves and split-second recoveries. As I saw it, it was a joyful exercise with rapidly changing vignettes - the intense faces of the competitors, the lightning speed and agility, the volatility of the men, aggressive at one moment, arms around each other in camaraderie the next, anger flaring at a dispute, then laughter coming from deep inside, full, unqualified.

Young boys looked on in a circle of awe. The throbbing berimbaum was a constant. And then suddenly the action dissolved, as if it had never taken place , and the street was empty. The spirit had changed.

So much happening all at once, flowing, changing. It was life lived on all sides to the full.

There is in contrast a certain quiet to life along the sea. But the sea pervades the life of the city. The very name Bahia means bay; the Bahia de Todos os Santos is the largest bay in Brazil. Five massive 16th- and 17 th-century forts stand in mute testimony to the former importance of the coast.

Each is different in shape and presence. The round towers at Monte Serrat are like those at Cartagena in present-day Colombia, the masterpiece of Spanish military architecture in the Americas. They overlook a long, low white marble wall ornately carved with flowing openwork circles. The wall stretches out along the sea on a spit of land and seems almost a strand of 18th-century Portuguese culture, archaeological evidence, between sea and unpaved shore. Leaning casually against it when I visited Monte Serrat was a small boy with pure African features and a barely contained energy, his face mobile with curiosity, laughter, and contemplation.

To the north of the huge bay stretch long white beaches, some of the most famous and beautiful in Brazil: Itapoa, Arembepe, Itacimirim. Along them and many small harbors in the elaborately indented coastline of the bay, the boats of fishermen move in and out with a slow rhythm like that of the sea, bringing back to Bahia the ingredients for the famous moqueca, a local fish or seafood stew based on African flavors.

Saveirosm and houseboats reflect color and white in the small main harbor of Bahia, and the undulating streaks of color against the dark waves are echoed in the long, thin lines of the indigenous dugout. Slender, seemingly fragile craft, tapered at each end, wonderfully picturesque to the tourist eye, dugouts are part of the daily life in Bahia. I watched early one morning as two sinewy old men brought one into the main harbor and unloaded a small catch of fish. They moved with beautiful, slow, and deliberate grace in tune with the sea. Always, in Bahia, the sea.

Nature and culture interplay here. One of the wonders of the city is watching color and light change on the beautiful old colonial architecture. Inside the 16 th-century Convento do Carmo, the glare of midday reflects in a muted sheen on the wide dark boards of the polished floors and from every contour of the sparsely placed old settles, giving the high white walls and narrow timbered ceilings of the halls a cool tranquility. But the interior would be bland and not Bahian without the squares of brilliant color beyond the tall, open doors at each end - the myriad pinks and reds of the faded, aged tiles of the roofs outside, abstract segments of pastel facades in pure bright stains.

But there is much more to the architecture and light of the city. When I came upon the church of the Palma, the long wide cobblestone square fronting it seemed larger than life, glaring white at midday with a shadow cutting a wide triangle across it. The old elegant building seemed to hover far away and on a plane above me, severe white with ornate cream trim. But when three small black boys in yellow shorts ran in and out of the sun in front of the elaborate doorways, the illusion was gone and the real substance of Bahia clear. The true wealth of the city is the combination of the people with the magnificent setting.

At dusk in the Pelourinho, the old square that is designated by UNESCO as one of the most important examples of extant colonial architecture in the world, the subtly varied facades radiate saturated pastel from behind luxurious grillwork. The last light splashes the shadow of one balcony at an angle inside the semidarkness of a white room with green shutters, a Cubist painting. Across the street, a muted interior light creates a lavender square in the center of a delicate, faintly peeling light-peach facade. Down the steep hill, past what I know to be the blue and white church of Nossa Senhora do Rosario dos Pretos, now a twin-towered black baroque shape, is a collage of pink, yellow, and red roof lines still lit by the sun.

There is a soft languor in the old buildings at dusk. It is easy to forget that they were built for a different time and social order. Until the end of the 18th century, Bahia was the most important city south of the Equator, a major cultural, economic, and political center. But nothing seems incongruous or jarring in the soft black voices and the casual habit people have of sitting on stoops. Bahia is never a museum. In the houses of Lisbon tiles, behind the elaborate marble cornices hidden in side streets off the square, life is lived, not stored safely away and protected.

There is no disjunction, but rather a great rightness that the Pelourinho is used and alive. It suggests a richness of living, an incandescent quality. This is perhaps the reason that Brazilians say ''God is a Brazilian.'' And perhaps the reason Jorge Amado told me that ''in Bahia, the people dance, and God is among them.'' Practical details

The Convento do Carmo, renovated into a hotel, is an excellent place from which to visit Bahia. On a cliff overlooking the sea a few blocks from the Pelourinho, it is the only top hotel in the center of the old city. Rooms are furnished in period antiques. The price of a double is $50 high season (December to March) and $40 low season, and includes a Brazilian a lavish breakfast buffet of tropical fruit, cold meats and cheese, hot eggs, bacon, sausage, and variety of breads.

The other top hotels in Bahia are located directly on the beach several miles outside the city, and rates are approximately 25 percent higher. Varig Airlines has daily flights from New York, connecting through Rio de Janeiro. Round-trip economy fare is $1,412 (APEX $1,205, GV2 $979). Varig also has a direct flight to Bahia from Miami once a week on Sunday, returning Friday. For further information contact the Brazilian Tourism Authority, 230 Park AVenue, New York, N.Y. 10169 (212-286-9600).