For its part, the federal government has spent relatively little to advance cleanup technology for spills.

Congress appropriated only about one-sixth of the $30 million in research grants to universities authorized under the Oil Pollution Act of 1990 after the Exxon Valdez, according to the Coastal Response Research Center.

The Bureau of Ocean Energy Management, Regulation and Enforcement - which was known as the Minerals Management Service until this month - collects $13 billion a year in oil drilling royalties. But the agency has been spending between $6 million to $7 million a year since 1995 on oil spill research.

And the Coast Guard's annual oil spill research budget has steadily dropped from about $5.6 million in 1993 to about $500,000 for each of the past four years.

U.S. Rep. Brian Baird (D-Wash.), who recently held hearings on oil spill cleanup technologies, said there hasn't been much federal spending for cleanup because the political pressure is to drill for more oil.

"Our priorities have been about how to extract more oil in greater volumes and for greater profits, and there haven't been corresponding priorities on how to do so safely and how to prepare if there is an accident," he said in an interview.

BP also has scrambled to try different cleanup techniques since the Deepwater Horizon rig exploded April 20, killing 11 workers and creating one of the U.S.'s worst environmental disaster.

The company recently ordered 32 centrifuge devices made by a company co-founded by Hollywood actor Kevin Costner, who had invested about $24 million in the project. The company says the largest of the devices can process about 210,000 gallons a day, separating gunk from water.

Deployed on barges, the centrifuges are intended to help skimmers work more efficiently by letting them unload the oil and water mix and cleaning it at sea instead of returning to port each time the tank is full.

Advances in drilling technology have enabled a boom in exploration and drilling in deep waters, where lower temperatures and higher pressures require sophisticated equipment.

"We've pushed the envelope more and more on offshore drilling in deep waters," said Nancy Kinner, co-director of the Coastal Response Research Center, a partnership between the University of New Hampshire and the National Oceanic and Atmospheric Administration.

Yet, she said, not much is known about how to collect oil from deep sea spills or how chemical dispersants used to break up oil behave at such depths.

Oil spill experts say that despite some improvements in containment booms and skimmers, they're still limited in what they can do. Booms generally work best in calm weather and waves, and need lots of maintenance.

In Barataria Bay, absorbent boom placed around numerous marshy islands didn't stop oil slicks from reaching wetlands. Some sections of boom were torn apart or doubled over. The stems of marsh grasses and other vegetation near the edge were stained dark brown with oil.

"In many case, all we have is that very basic technology and of course we use it," said Dennis Takahashi Kelso, vice president of the Ocean Conservancy and former Alaska Commissioner of Environmental Conservation during the Exxon Valdez spill.

"We ought to do better though if we take seriously how harmful a spill can be," he said.