ABC News

By JEFFREY KOFMAN

For 86 days, oil spewed into the Gulf of Mexico from BP's damaged well, dumping some 200 million gallons of crude into sensitive ecosystems. BP and the federal government have amassed an army to clean the oil up, but there's one problem -- they're having trouble finding it.

Watch 'World News' for the latest coverage on the Gulf oil spill.

"That oil is somewhere. It didn't just disappear," said Plaquemines Parish President Billy Nungesser.

Salvador Cepriano is one of the men searching for crude. Cepriano, a shrimper, has been laying out boom with his boat, but he's found that there's no oil to catch.

"I think it is underneath the water. It's in between the bottom and the top of the water," Cepriano said.

"It is becoming a very elusive bunch of oil for us to find," said National Incident Cmdr. Thad Allen.

Skimmers Pick Up Less Oil

The numbers don't lie: two weeks ago, skimmers picked up about 25,000 barrels of oily water. Last Thursday, they gathered just 200 barrels.

Still, it doesn't mean that all the oil that gushed for weeks is gone. Thousands of small oil patches remain below the surface, but experts say an astonishing amount has disappeared, reabsorbed into the environment.

"[It's] mother nature doing her job," said Ed Overton, a professor of environmental studies at Louisiana State University.

At its peak last month, the oil slick was the size of Kansas, but it has been rapidly shrinking, now down to the size of New Hampshire.

Today, ABC News surveyed a marsh area and found none, and even on a flight out to the rig site Sunday with the Coast Guard, there was no oil to be seen. The light crude began to deteriorate the moment it escaped at high pressure, and then it was zapped with dispersants to speed the process along. The oil that did make it to the ocean's surface was broken up by 88-degree water, baked by 100-degree sun, eaten by microbes, and whipped apart by wind and waves.