No oil could be seen in the water during Obama's helicopter ride from New Orleans, over Louisiana bayous, to Port Fourchon.
That changed when he arrived at Fourchon Beach, however.
A shirt-sleeved Obama walked to the water's edge, stooping as Adm. Thad Allen of the Coast Guard explained what he was seeing.
The beach, sealed off with crime-scene-style yellow tape, is one of the few sandy stretches on Louisiana's coast, where most is marshland. Obama called reporters traveling with him to the water's edge and picked up a few pebble-sized tar balls.
"These are the tarballs that they're talking about," he said. "You can actually send out teams to pick up as they wash on shore.
He added, "Obviously the concern is that, until we actually stop the flow, we've got problems."
After about 15 minutes at the beach, the president headed to nearby Grand Isle for a formal briefing from Allen, who is overseeing the spill response for the federal government. At intervals along the way were handwritten wooden signs stuck in the sand with "BEACH CLOSED" in black block letters. One woman held up a sign saying "Clean Up the Gulf" while two people played guitar and sang.
Obama was joined there by the governors of Louisiana, Florida and Alabama. He was spending a total of about three hours in the region.
Allen said on CBS' "Early Show" that the cleanup already is enormously difficult. "It's a real, real tough challenge, especially in the remote areas where you have marshlands involved," he said.
The oil rig leased by BP exploded April 20 and later sank, killing 11 people and releasing millions of gallons of crude oil into the Gulf. There is deep frustration along the coast, increasingly felt in the country at large as well, at the inability of BP and the government to stop the massive spillage of oil into the water.
BP PLC is using what is called a "top kill" procedure to try to stop the leak by pumping in heavy mud. If it doesn't work, something BP says will be known within a couple days, Obama's political problems will only compound.
On Thursday, Obama acknowledged his administration could have done a better job on several fronts. They included misjudging the industry's ability to handle a worst-case scenario, not moving sooner to end "cozy and sometimes corrupt" relations between the oil industry and government regulators, and not getting a better estimate on the amount of oil gushing from the broken well.
He spoke in sometimes personal terms about his ownership of the crisis.
"I take responsibility. It is my job to make sure that everything is done to shut this down," Obama said. "This is what I wake up to in the morning, and this is what I go to bed at night thinking about."
He also announced a series of new restrictions on oil drilling projects. And the first political casualty of the spill came Thursday when Elizabeth Birnbaum, the head of the Minerals Management Service that oversees offshore drilling, resigned under pressure.
Locals suffering the effects of the oil that is soiling birds and darkening beaches had mixed feelings about Obama's trip.
"He'll have a better idea of what he needs to do or get other people to do," said Donald Lefort, 41, a convenience store clerk in Venice, La., a staging area for containment efforts.
A frustrated Larry Freman, 72, who was cleaning up around his vacation home on Grand Isle's main drag, usually packed with tourists for the holiday, said Obama should stay home.
"He's wasting his time," the oil business veteran said.
In Washington, Secretary of State Hillary Rodham Clinton said the government was still evaluating offers from 17 countries and organizations for such things as technical expertise and equipment. The Coast Guard hasn't yet accepted any of the foreign help, but BP has accepted booms and skimmers from Mexico and Norway.