Is he a liar or just dumb? Looking at the money that he’s raking in plus the fact that he still holds his job tells me he’s not a stupid person.

“The oil is on the surface,” Tony Hayward, BP’s chief executive, said last week. “There aren’t any plumes.”

Descriptions of the plumes from the two groups of scientists are filling in details of one of the most remarkable findings to come from the disaster: the realization that much of the oil in a deepwater blowout may remain below the surface.

The scientists say the plumes are not bubbles of oil, as many people have imagined them, but consist of highly dispersed or dissolved hydrocarbons. In some spots, enough oil is present to discolor the water, but in most places, water samples come up clear. Yet the dissolved hydrocarbons show up vividly on instruments, and they can be smelled in some samples.

“This so-called invisible oil, which people tend to have a hard time grasping, is detectable clearly using analytical methods,” said Ernst Peebles, a University of South Florida oceanographer who helped carry out the research.