MUYNAK, Uzbekistan— The life of Kubeisin Ikmitulayev has been just long enough for him to watch the death of one of the world's largest inland seas.

''When I was a small child I used to go swimming all the time,'' said Mr. Ikmitulayev, who recently celebrated his 30th birthday. ''The water came right up to our backyard. But by the time I was 8 years old it was too far away to walk.''

Mr. Ikmitulayev knew Muynak when it was a thriving port and popular resort on the Aral Sea. In his lifetime the Aral, once at 25,000 square miles the world's fourth-largest lake, has shrunk by more than half, to 12,000 square miles.

Today Muynak, whose population has dropped to 28,000 from 45,000 in the last 30 years, is a desert town. The water that used to flood the streets on stormy days is now more than 70 miles away.

On what was once the seabed, abandoned ships lie in a sandy graveyard, a grim reminder of how quickly such catastrophes can overwhelm communities and nations.

A small museum displays relics. Its main hall is dominated by a panoramic oil painting that shows fishermen repairing their dories while draggers pull away from piers and gulls hover. On display are anchors, nets, fish traps -- artifacts that evoke a poignant sense of loss.

For thousands of years Central Asia's two great rivers, the Amu Darya and the Syr Darya, fed the Aral. But as this region became the main Soviet source of cotton, a maze of irrigation canals was built.

Much of the diverted water was lost to evaporation and seepage, because the canals were neither covered nor lined. After those losses and the huge amounts of water that the cotton plantations absorbed, only a trickle was left to feed the Aral.

And even that amount may have done more harm than good. It was contaminated with the pesticides and other chemicals that were being sprayed on cotton and rice fields. These chemicals settled on the seabed, and now that much of the sea has evaporated, windstorms carry them through the streets of Muynak and hundreds of miles beyond.

''Dust storms pollute the air we breathe and the water we drink,'' said Orinbey Yusekepov, a local doctor. ''We are seeing a very high incidence of anemia, especially among children. Cancers have increased. Stomach and intestinal diseases are very common. People's kidneys and livers cannot stay healthy in an environment like this.''

All five Central Asian countries that emerged in 1991 with the collapse of the Soviet Union are affected by the cataclysm at the Aral Sea, which is divided between Uzbekistan and Kazakhstan. Leaders of all five have acknowledged the scope of the disaster. ''Never before has such a case been witnessed in history,'' President Islam Karimov of Uzbekistan wrote in a newly published book about Uzbekistan's problems. ''In the lifetime of only one generation, the death of a whole sea.''

''Not long ago triumphant trumpets celebrated the increase in new irrigated land reclaimed from des erts,'' Mr. Karimov wrote. ''This irrigation water was taken from the Aral, and it was 'forgotten' that this was 'drained blood' from this sea.''

Although the Presidents of the five Central Asian nations, which also include Kyrgyzstan, Tajikistan and Turkmenistan, have urged action to protect what remains of the Aral, none are optimistic. Mr. Karimov has warned that saving it will prove ''complicated or even impossible.''

Scientists and political leaders agree that the only hope for halting the seemingly inexorable shrinkage would involve drastic conservation. But because all the Central Asian countries require great amounts of water for irrigation and power, none are ready to take radical steps.

Making a major cut in the amount of water taken from the Amu would mean ''a big drop in agricultural production, widespread unemployment and tremendous social dislocation,'' said Ospan Kariansakov, an Uzbek Government official.

Environmental groups, banned during the Soviet period, have begun drawing up preservation formulas. But so far, there is not even a system to measure how much water is being taken from the two rivers and by whom, much less an agreement to reduce consumption.

''At the moment there is no strategy, only chaos,'' said Timur Razzakberdyev, chairman of an environmental group called Aral-S O S. ''The problem can only be managed if the five countries agree to stop considering water as national property.''

Although the countries have other resources, they are unable to take the sweeping steps necessary to restructure their economies away from water-intensive agriculture.

''If these countries are going to change their ways and cut their water use,'' said Sardar Gasanov, a scientist at the United Nations Development Program here, ''they need to industrialize or at least start growing other crops that don't need as much water. That is a huge project.''

The problem has led to a spreading sense that it may be too late to save the once-rich Aral.

''I can remember when houses in Muynak would wash away in storms,'' Mayor Utemurat Kalmuratov recalled. ''Our fishing boats used to bring in 30,000 tons of fish each year. We had 300 boats and 1,000 fishermen. But if things keep going as they are, the whole sea will be gone in 20 years.''

Photo: On the Aral seabed, abandoned ships are a grim reminder of how quickly constant overuse and pollution can bring catastrophe to a region. (Staton R. Winter for The New York Times Map of Uzbekistan showing location of Muynak: Muynak, which was on the Aral 30 years ago, is now 70 miles away.