VENICE, Italy -- The sirens wailed, the waters of the Adriatic Sea crept into St. Mark's Square, and a cold chill struck every Venetian who had suffered through the historic floods of 1966.
It was Nov. 4 -- 25 years to the day after the unwelcome tides rose more than 6 feet above their normal level, wreaking devastation on the centuries-old buildings and monuments of this magic city built on tiny islands.
"Acqua alta" is Italian for "high water," the strange phenomenon that visits this decaying Renaissance capital with increasing regularity.
Usually occurring in the fall and winter, the phenomenon is the product of rain, barometric pressure and "sirocco" winds from the Sahara, which raise the water level in the northern Adriatic.
Venetians are hardly strangers to flooding of their canal-laced streets and squares. Apart from its anniversary visit, this year's Nov. 4 high water was unexceptional, the fourth flood of the season.
Some ever-present tourists, a mainstay of the city's economy, delightedly sloshed barefoot through knee-deep water. Residents took it in stride, donning knee-high rubber boots or hip waders and going about their business.
Wooden catwalks were erected on scaffolding in St. Mark's and other low-lying squares, enabling pedestrians to move about with dry feet.
And once again, concerned citizens all over the world took notice of the natural and man-made forces that conspire, at an accelerating rate, to destroy Venice. A quarter-century after the 1966 catastrophe, much remains to be done.
More than two-thirds of the city's buildings, many of them 11th- and 12th-century palaces and churches, have damaged bases. More than one-third of the plaster on their walls is affected.
In October, after high water assaulted Venice for the second time in a few weeks, Mayor Ugo Bergamo again called for more money from the Italian government.
"I will ask for financing that will guarantee the beginning of a physical rescue process not only against high tides but also the damage caused by motorboats," he said.
Early in this century, St. Mark's Square, the lowest point in the city, flooded an average of seven times a year. Now the average is 40 times a year.
Along with the world's oceans, the level of the Adriatic has been rising. Since 1900, it has risen more than 4 inches.
If predictions are correct, it will rise even more because of global warming.
At the same time, Venice has sunk nearly 5 inches. The drop in land level is attributed to water wells in mainland suburbs. When pumping was prohibited in the 1980s, subsidence stopped.
The city of Venice is a 2-square-mile dot in a 212-square-mile lagoon. Its population is steadily dwindling -- from 175,000 in 1971 to about 78,000 today -- as residents move to more habitable, affordable places.
A complex sequence of ecological disasters, brought on by overdevelopment, has polluted the lagoon to the point where action is necessary to save it.
A broad-based program was launched in 1987 by the New Venice Consortium, a group of 26 Italian companies created by a 1984 national law to confront the daunting challenges.
Working closely with the consortium has been the 24-nation, Paris-based Organization for Economic Cooperation and Development, which just finished an extensive three-year study of the Venice coastal zone.
The consortium's most ambitious and most publicized project, appropriately called Moses, would hold back Adriatic tides when they become too high.
Moses is a prototype for a proposed system of nearly 80 submerged gates beneath the three entrances to the Venice Lagoon.
During high tides, the gates would rise automatically out of the water to form a barrier that would keep the tides from flooding the lagoon.
Consortium officials say that the prototype works and that construction of the system could begin as early as 1992 and be completed by 2000.
But most of the money hasn't been made available by the Italian government. The estimated cost of all consortium projects is about $4.2 billion.
Francesco Bandarin, head of the consortium's research office, reflects the frustration over government inaction.
"Either the government allocates the money," he told National Geographic, "or we find another way of financing this project. It's very much up in the air."
"Venice Is Flooded by Indifference" read the headline of an Italian newspaper in August.
"The government has to realize that without continuous financing, Venice will die," Luigi Zanda, chairman of the consortium, told the newspaper. "We have not received any financial help since 1988."
In the historical center of Venice, the famed canals double as a sewer system that is decades overdue for dredging.
Summer brings algae. In the dry, sunny summer of 1988, green "blooms" from agricultural chemicals clogged the lagoon, emitting noxious hydrogen sulfide vapors and breeding billions of insects that stopped trains and planes.