SIPADAN ISLAND

The corals that come in every color hang like flowers in a boutique. Drifting with the current by this gardenlike reef, a diver spots a green turtle gracefully flapping its flippers.

The gentle creature lets her touch its shell. Together, woman and reptile dance an underwater waltz, twirling each other 60 feet below the crystalline blue surface.

Sipadan Island is a scuba-diver's paradise. In Depth magazine rated it one of the world's five best dive sites and the world's best beach dive in 1993 and '94.

The island is expensive and difficult to reach, but that's not dissuading diving enthusiasts who scour the globe in search of that rarely seen school of hammerhead sharks or field of giant clams.

A seven-day package deal (excluding airfare) from Kota Kinabalu, capital of the Malaysian state of Sabah, costs $1,325, says Ken Knezick, head of Island Dreams Travel in Houston. From the United States, travel time is about 2-1/2 days by plane, bus, and boat or helicopter.

But ask any diver who's been there: ''Is it worth it?'' And you'll get a resounding ''Yes.''

Burt Jones, a marine-life photojournalist who has spent more time there than any other American photographer, calls the 30-acre spit of sand and jungle atop an underwater volcano ''the Grand Cayman or Cozumel of Southeast Asia.''

''It is one of the most enchanting places I've ever been to,'' says Stephen Harrigan, a 32-year diving veteran and author of the book, ''Water and Light: A Diver's Journey to a Coral Reef'' (Houghton Mifflin, 1992). ''There are more living things than I'd ever seen - the turtles, white-tip reef sharks, staggering amounts of fish,'' he says.

Environmentalists agree. In 1933, the island was designated a bird sanctuary for its Nicobar pigeon and other birds. But it's best known for its green and hawksbill turtles.

It's common to see at least a half dozen (and usually many more) on one dive. The greens, in particular, make Sipadan a mating and nesting home. To protect them, the Sabah Ministry of Tourism and Environmental Development's Wildlife Department stipulates that tourists must be accompanied by a ranger when walking the beaches at night, the time turtles lay their eggs.

''No other spot on the face of the planet has more marine life than this island,'' the World Wildlife Fund proclaimed in 1980.

Five years later, Ron Holland of Britain learned for himself. He told explorer Jacques Cousteau about the island, who brought a crew to film what Cousteau called ''an untouched piece of art,'' the kind he had not seen in 45 years.

At that time, hard-core divers camped out on this backwater to dive the 2,800-foot reef wall, which drops off into the abyss just yards from shore. But in 1990, an outfit named Borneo Divers, started by Mr. Holland, put up a modest thatched-roof resort. That year, 1,024 guests stayed there.

Since then, word-of-mouth, In Depth accolades, marketing by Borneo Divers agents, and magazine and newspaper articles have contributed to increased development and a tourism explosion.

Holland reports that 2,731 people will stay at his resort this year. The island's hotel bed count is up to about 130, after three Malay- and Chinese-owned operators built resorts. Adding to the traffic are visitors to nearby Pulau Mabul.

Fred Siems (no relation), an early Sipadan diver and Malaysia Airlines sales manager, says that close to 5,000 divers will visit in 1995. But, by all accounts, the diving off this island is still superb. Development has reduced visibility from about 100 feet in 1990 to 40-60 feet today, but marine life is more abundant.

''I've seen a larger density of fish,'' Mr. Siems says. ''They're more approachable, not afraid of divers. They know it's safe [from fishing] here.''

The big question on divers' minds: Will the island go the way of Tahiti and Cancun and be overdeveloped?

''If development isn't curtailed, the island will suffer and, in the long term, so will the marine life,'' Holland says. The government tries to limit development, but enforcement is difficult, he explains. ''All rules and regulations that have been enforced, as far as protection of the marine life and fauna, were instigated by Borneo Divers.... But we could not control the [overall] development, only in our own area.''

Twice in two years, the Wildlife Department has ordered construction to halt. Borneo Divers complied, but the other resorts did not. Two new ones even tried to spring up. Enforcement officers sent to dismantle buildings constructed after the first order was issued were stopped by an injunction filed by a new operator. The courts rejected the injunction, but the operator appealed.

There are plans to make Sipadan part of a marine park. But an obstacle remains: Indonesia is contesting Malaysia's ownership of the island. The case will be heard by the World Court, Siems says.

The turtle-egg issue, however, has reached a happier conclusion. At Borneo Divers' urging, resorts are paying the man who has traditionally held the turtle-egg-collecting rights on the island a total of $100,000 not to collect eggs until 1997, thus preserving the turtle population.