Globs of sticky brownish ooze soil miles (kilometers) of sensitive shoreline and marsh from Alabama to Louisiana. Pelican rookeries are awash in oil. Oyster beds and shrimp nurseries face certain death. All the while, long, slender barriers intended to protect the shoreline float twisted, tangled or sometimes just broken apart, unable to stop the creeping crude.

Since last month's rig explosion and spill of millions of gallons of oil into the Gulf of Mexico — now the largest spill in U.S. history, surpassing the Exxon Valdez — more than 3 million feet (900,000 meters) of so-called boom has been deployed along the coast. But it's not a fail-safe method of keeping the oil from washing ashore. It's not always sturdy enough, and high winds and waves can send the slime cascading over the barriers.

The key line of defense is sometimes defenseless itself against the elements.

"Even if it's working properly, the best it will do is move the problem somewhere else," said Doug Helton, incident operations coordinator for the National Oceanic and Atmospheric Administration's Emergency Response Division.

"It might be moving it somewhere that's not boomed or it might be moving it 100 yards away where there's a failure in the boom," Helton said. "The use of booms is just one tool but all the boom does is deflect oil, and that's if it functions properly."

BP says it has spent more than $800 million on cleanup and containment efforts since its Deepwater Horizon rig exploded April 20 and sank 50 miles (80 kilometers) off the Louisiana coast. Since then, an estimated 19 million gallons (72 million liters) or more of crude has spewed into the sea.

While BP couldn't immediately provide a figure for how much money has been spent purchasing and deploying the booms, industry estimates put costs around $20 a foot (more than $60 a meter) for the basic product — totaling at least $60 million just to buy it, not to mention the cost to hire people to deploy it.

Experts say while the boom isn't perfect, it provides one necessary line of defense. It also offers a psychological boost to those who feel helpless.

Because the oil spill is so widespread, manpower needed to maintain the boom and regularly collect oil from its constraints is stretched thin, Helton said. And as the barriers break apart, he said, response time to repair them must be quick because once the oil seeps past, it's a losing battle.

The spill's impact on shorelines now stretches across 150 miles (241 kilometers), from Dauphin Island, Alabama, to Grand Isle, Louisiana, and has begun to creep inland into sensitive marshland.

"Normally, a spill would affect a smaller geographic area so you'd have more people per linear mile of boom to maintain it, but here the pressure was on to get the boom deployed," Helton said. "It's a difficult situation and people have very high expectations.

"There's no silver bullet," he added.

Regardless of the setbacks, BP spokesman John Curry said the booms are still proving to be an effective tool.

"Booms, by and large, do work. They're not fail-safe, but they're our best protection to contain the oil and protect the coast," Curry said.

Stephen Reilly, CEO of Slickbar Products Corp., one of the world's largest manufacturers of oil spill equipment, including boom, acknowledged the product has limitations based on wind, waves and currents.

He said Slickbar has so far provided several hundred thousand feet of boom to the Gulf oil spill effort, and calls it "absolutely worth it."

"You have to put something in there," Reilly said. "You have to at least make an attempt to deflect it away from these sensitive areas ... The key is to at least try to contain it."

Inexperience may also be taking a toll on the effectiveness of the booms, said Ed Overton, a Louisiana State University professor of environmental sciences.

Hundreds of people, including fishermen and shrimpers who have never deployed boom, have mobilized to help.

"People are frustrated and they want to do something so they say, 'I'll go out and lay the boom.' But if you don't know what you're doing, you're not going to do it right," Overton said. "I'm certain there's a significant percentage of boom deployment that is basically a wasted effort. I've seen shrimp boats just pulling boom and it's not doing anything."

Jefferson Parish Sheriff Newell Normand said neither BP nor the federal government is listening to the locals, who know these waters, about where to lay the booms.

"We're still deploying boom in areas that in many cases don't make sense to us, but that's where they want it," Newell said. "They're not asking us for input. Someone else is commanding this ship and they're not taking input from the local commercial fishing industry that knows these waters better than anybody.

"We don't have a command post that's totally unified where they're actually listening to the locals," he added.

But even beyond the environmental effort to contain the oil, effective or not, the booming serves another crucial purpose, providing a psychological boost to those who feel helpless, Overton said.

"It's an ecological incident but this is also a sociological disaster," he said. "It's helping people think they're helping the environment, and there's a lot of good to that. I'm talking about getting to their psyche. They don't know what the future will bring.

"Booming is not just about protecting the environment," he added. "It's also to help the people and that should not be considered trivial or a waste of time."

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Associated Press writers Matthew Brown, Jason Dearen and Greg Bluestein and Video Journalist Jason Bronis in Louisiana, and Holbrook Mohr in Mississippi contributed to this report.

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