Looking for evidence of the world's greatest oil spill on South Padre Island is a little like looking for the Loch Ness Monster in Scotland. Everyone says they saw it, have stories to tell of sheen or globules, and even sing songs and sport T-shirts celebrating the Tar Babies of '79. But the oil is now nowhere to be seen and, in fact, according to Coast Guard sources, it's moving rapidly beyond the continental shelf and away from the Texas shores.

During my visit the slick, estimated at 400 miles long and now 200 miles south of Texas tourist centers, was still being reinforced by a blown-out well off Campeche, Mexico, spilling nearly 10,000 barrels a day into the Gulf of Mexico. The three plans to stop it (capping it, drilling pressure relief wells into the oil chamber, and plugging the pipes through which the oil is pouring into the Gulf) all has failed. (On Oct. 16, Mexican and American experts finally succeeded in capping the well and drastically reducing the flow, and were expecting soon to finish the job and cut it off completely.)

The mass of oil, reacting with salt water and combining with sea growths and animals, never arrived on the nearby white sands of the Texas tropical coast, with its Miami-like climate but much sparser population. The slick did send out raiding parties of pollution which hit the beaches up and down the chain of barrier island on the Texas Gulf. The landing on the two pieces of Padre took place over a two-week period in August. They were met, each time, by a determined Coast Guard equipped with the latest in ecological defense equipment, shovels and wheelbarrows.

For two weeks oil blobs, brown messes like congealed froth and a castor-oil sheen came in. Tourist rushed to the check-out desks an no one replaced them: August, normally the busiest season on the island, was a tomb. September ran 40 percent behind normal, and October was likewise lagging

Ironically, the coast now is as clear and clean as last year. The water, clear and sandy in the shallows, green in the middle distance and deep blue to the limits of the eye, rolls in on spick-and-span but empty dunes. Only small crowds can be found in the new Hilton, trying the Jacuzzi near the pool, or at the fortress-like, "Hurricane-proofed" Bahia Mar Hotel, or at Louie's bayside over-the-water dining piers, having sundowners and moonuppers in the balmy breeze.

The local tourist bureau is running scared, according to Laura Peters, its representative. The bureau has instituted two toll-free lines, in-state (1-800-292-7508) and national (1-800-531-7406), over which it will convey to interested parties the present whereabouts of oil slick or algae patch (as determined by Coast Guard helicopters), temperature, water conditions and where and when the fish are biting -- or anything else of interest.

Special packages of holiday bargains have been assembled for nearby residents who have long taken Padre's 70-degree winters for granted, since the same sun and southerly breezes nourish orchards of oranges, grapefruits and lemons all over the Rio Grande Valley and permit winter vegetable crops as well. The locals have always been skeptical of the $40-a-day grandeur of the Hilton and Bahia Mar, and are more likely to truck in their own refreshments and entertainment in styrofoam coolers. Now they, and visitors from further away as well, are being told of more modest eating establishments on the island, inexpensive places to bed down: The tourist trade disaster has made things more democratic.

The$10 special still stars at the Big Three on the tip of Texas: seafood bisque at Bahia Mar, shrimp with wine sauce at the Hilton, and the gut-busting buffet of five kinds of salad and 10 kinds of fish and meat at Louie's Backyard. But now, since the spill, the tourist bureau directs you as well to a bean sprout sandwich at the Dockside Deli; a shrimp on a bun, volleyball and longnecks at Blackbeard's, or the catch of the day in a submarine sandwich at Ted's or the Jetties on the Brownsville Ship Channel.

Across the new causeway connecting South Padre Island town with Port Isabel one finds the Champions General Store and Restaurant -- enlivened nightly by the Tired Businessmen's Dixieland Band and weekends by local Texas funk bands -- an the Yatch Club, both four-star establishments. Down the road about 20 miles lies Brownsville-Matamoros for shopping, bullfights, horse racing and sightseeing. All around lie the fertile waters and fields where visitors can catch or pluck their meals, with both fishing and fruit harvesting getting better as the winter goes on.

Up until the present, the state and the local tourist bureaus have done very little advertising for visitors; people just passing through would stop, on their way to Mexico or on fishing trips out of the deep-water Brownsville port. They told their acquaintances and word of mouth alone brought people flocking in and created a small boom in condominium and retirement home building on Padre Island. After Hurricane Beulah in 1974 failed to shake the Bahia Mar and other structures on the waters, and after the Federal Government guaranteed hurricane insurance for the area, building began in earnest. Today construction is evident all along the sands, with most of the multi-story condominiums sold out before construction starts. South Padre Island is on its way to becoming a major oceanside attraction.

The oil slick will slow but not stop progress, which some see as the ultimate danger to the island. The most famous local resident, Ila Loetscher, better known as The Turtle Lady for her kindness to all sea turtles down on their luck, is a symbol of the environment. kShe has slowly lost ground in her 30 yers of wildlife preservation efforts.

Loetscher recalls when she first set up a turtle hospital here, she could let her charges out into the bay waters between the island and the mainland for a run. She had a turtle ranch and corrals in the healing, calm lagoon, but had to move hastily when causeway construction stirred up bottom mercury deposits that blinded and then killed several of her shelled friends.

Then she moved the dozen or so surviving patients into tanks in her backyard and house. She and an organization called Seaturtle Inc. began trying to save the Kemp ridleys, which is a sea turtle with a jeweled shell, an endangered species, by importing eggs and raising them on the South Padre beaches. The eggs were hatched out on the sands not too far from her home, the small turtles went to sea, and eight years later were supposed to return to Padre to deposit their progeny.

Eight years have now gone by since the launchings, but dune buggies and construction vehicles frighten the returning animals and probably crush more than a few of them. The species-saving effort seems largely doomed.

Not that Loetscher and the other conservationists are giving up: Once again they are moving, this time to the remote reaches of North Padre Island, across a fish channel and unreachable except by four-wheel vehicles from the north. Sixty miles have been set aside as a National Seashore, and there once again the turtles are being released into the sea, imprinted, with the hopes that they will establish a breeding cycle and save themselves.

The oil slick may be a barrier to returning turtles and fish life says, Loetscher, as she discussed the record catches of fish being reported on the southern coast: Schools of fish may be trapped by the spill and forced inland. The turtles, further out, may not reach shore and will probably be scared off or killed if they approach. A few of them have washed in, multilated or downed, probably after being caught in fishing or shrimp lines.

If the oil spill has been herding the fish in and the turtles out, if fish -- as Red Adair has said -- are nibbling at the edges of the slick, then next year will probably be Padre's "Silent Spring." The oil flow will probably stop soon and in time the oil in the ocean will disappear, though lawsuits have been filed against Mexico, and experts estimate that it may be a few years before they will know the full extent of the environmental damage. Migratory birds and the winter Texans, mostly from the Midwest and Canada, may continue to meet in the marshes nearby; the walls will rise on yet more rows of condominiums, and new roads will be scratched across the dune line to connect plots half under water to the main shopping area (the land was subdivided on the expectation that the receding ocean will continue to recede, thus extending the shore and leaving more land high and dry).

Another spill, more condos, a more severe hurricane -- Padre's future hangs by a thread. But no one is worried about the future of Padre Island -- it's the drop in business that's getting them, though few seem to even care much. The present, a wonderful winter, lulls them. The long evenings and the fresh air may do it to people. Even the Turtle Lady doesn't worry much -- though her personal view of the ocean could soon be blocked by construction, her project is moving once again.

For the next few months, Padre will be basking blissfully in the warm Texas sun.