http://news.yahoo.com/s/ap/us_gulf_oil_spill_plumes

BP PLC CEO Tony Hayward on Sunday disputed claims by scientists that large undersea plumes have been set adrift by the Gulf oil spill and said the cleanup fight has narrowed to surface slicks rolling into Louisiana's coastal marshes.

During a tour of a company staging area for cleanup workers, Hayward said BP's sampling showed "no evidence" that oil was suspended in large masses
beneath the surface. He didn't elaborate on how the testing was done.

"The oil is on the surface," Hayward said. "Oil has a specific gravity that's about half that of water. It wants to get to the surface because
of the difference in specific gravity."

Scientists from several universities have reported plumes of what appears to be oil suspended in clouds stretching for miles and reaching hundreds of
feet beneath the Gulf's surface.

Those findings — from the University of South Florida, the University of Georgia, Southern Mississippi University and other institutions — were based on
initial observations of water samples taken in the Gulf over the last several weeks. They continue to be analyzed.

One researcher said Sunday that their findings are bolstered by the fact that scientists from different institutions have come to similar
conclusions after doing separate testing.

"There's been enough evidence from enough different sources," said Marine scientist James Cowan of Louisiana State University, who reported
finding a plume last week of oil about 50 miles from the spill site that reached to depths of at least 400 feet.

Hayward said BP's efforts are concentrated on fighting surface slicks.

At the company's bustling Venice staging center, the embattled CEO tromped through the mud to inspect stacks of orange-colored booms being
deployed to protect Louisiana's fragile brackish marshes.

He said the company is pouring cleanup resources into Louisiana for a fight that could last months, and that the effort would continue until
"every drop" of oil is cleaned up.

Hundreds of workers already are set up in "floating hotels" at the mouth of the Mississippi River, from where they can quickly respond to slicks of crude once they are spotted in the marshes, Hayward said.

An estimated 18 to 40 million gallons of oil have been unleashed since BP's Deepwater Horizon platform exploded and sank last month, killing
11.