As the Gulf of Mexico oil spill hit the 100-day mark Wednesday, here are 10 big developments likely to influence future decisions on offshore exploration:

It doesn't all float: The massive slick has largely vanished - partly consumed by microbes and worked on by wind, waves and sun - but perhaps tens of millions of gallons may still be under water.

The discovery of vast deep sea plumes - thought to be the result of chemical dispersant reducing the gushing flow into tiny suspended droplets - has destroyed conventional wisdom about what happens when oil and seawater mix. Particularly when you add an unprecedented volume of chemical dispersants.

BP initially dismissed they were there.

Now, the plumes - likened to underwater clouds of mist - rank among the biggest cleanup concerns. Federal and academic researchers can't say for sure yet how big they are, what is likely to happen to them over time or whether the concentrations, which fade from strong around the well to barely detectable 40 miles away, are toxic to marine life.

Documents also said BP skipped a test to determine if cement had properly bonded to the well and rock formations, which would have been safer but taken 12 hours.

A little hustle would have helped: For weeks after the April 20 spill, BP was estimating the flow of oil at 5,000 to 20,000 barrels a day, and responded with a "top hat" containment device capable of sucking up only about 15,000 barrels a day. But by mid-June government scientists were saying the well was spilling 50,000 barrels a day or more, and the Obama administration demanded a bigger, faster response from BP.

BP finally started to hustle. Today it has 800 skimming boats, 4,300 other vessels, 114 aircraft, 3.4 million feet of boom and 24,800 workers. And it has unveiled the Ella G - a 280-foot-long supply vessel outfitted with four centrifuges capable of slurping up 800,000 gallons of oily water a day.

But now, of course, the well has been capped and there's relatively little oil to clean up.

It wasn't a heck of a job: The three-month oil spill may not wind up, as some critics charge, "Obama's Katrina." But the administration didn't exactly ace the Gulf Coast history tests either.

Like the Bush administration after the disastrous 2005 hurricane, the Obama administration was slow to grasp the scale of the spill and, in the first month, gave BP too much credit and leeway as the oil giant downplayed the threat and bumbled through failed attempts to plug the gusher.

NOAA, the lead science agency, also drew fire from many Gulf scientists, echoed by some congressional members. They contend the agency was slow to tap its expertise, slow to dispatch research vessels, and slow to push BP for flow-rate data that would have more quickly shown the blowout to be a disaster of historic proportions.

As the president's poll numbers plunged, the administration's multi-agency Unified Command made tougher demands, drawing $20 billion damage pledge from BP and a dramatically expanded capping effort.

Give spill-killing efforts macho names: There was the "top kill" for plugging the leaking well with heavy mud and cement from the top. And the "bottom kill" for plugging it 13,000 feet beneath the seabed.

"Top hat" described the small, cone-shaped funnel attached to a riser line that BP lowered over the spewing well early on. It didn't capture enough oil, so it was discontinued.

Then there was the "junk shot." To the heavy mud they added shredded tires, golf balls and other pieces of fibrous material in hopes of clogging the crippled blow-out preventer. Experts warned the idea was "exotic" and might not work. They were right.

Next: A "bullhead kill." Now that the blown-out well has a secure cap on it, a bullhead kill will pump in heavy mud and cement through existing pipes on the blow-out preventer, making it easier to complete the relief well everyone sees as the final answer to the spill.

Linguists debate which of these handy new terms will make it into next year's Oxford English Dictionary.

The Gulf may heal itself faster than we thought: When we fool with Mother Nature, sometimes she fools us back. Experts say up to 50 percent of spilled oil - the most volatile, toxic part - can evaporate within a week as the oil slick floats toward shore. Another portion can be eaten by naturally occurring microbes, especially in warm Gulf waters. "Oil is a natural product. It's inherently biodegradable," said Terry Hazen, microbial ecologist at the Lawrence Berkeley National Lab in California.

Even hurricanes can help. After the massive 1979 Ixtoc spill in Mexico's Bay of Campeche, Hurricane Frederic was credited with scouring tar balls off the Texas coast. Experts say a hurricane's egg-beater effect on the water might break up oil sheens into small oily particles more easily digested by microbes.

Even water's-edge marshes, crucial to sheltering juvenile shrimp and dampening the surge of hurricanes, have some self-healing abilities. Environmentalists visiting Louisiana's oil-soaked marshes already have spotted new green sprouts thrusting up through the black goo.

Regulators shouldn't sleep with industry: It took an epic environmental catastrophe to do what scathing government investigations, years of bipartisan criticism, sex-and-gifts scandals and a $10-billion bureaucratic bungle could not: force the dismantling of the federal agency that regulates the offshore drilling industry.

The once obscure Minerals Management Service had two main missions: To enforce drilling safety rules and to collect billions in royalties form the $1-trillion-a-year petroleum industry. It did neither well, costing taxpayers billions in unclaimed royalties and allowing the industry to largely set its own safety standards - a hands-off attitude that enable BP's disastrous blowout.

In one notorious case, two MMS employees were literally found in bed with the industry: There were cited, after an internal investigation, for having brief sexual relationships with oil company officials. The executives plied 19 employees in an MMS royalty office with gifts, booze, and golf and ski trips.

The agency is being broken up in the wake of the spill. The Obama administration promises to mend regulatory loopholes and end cozy relations - pledges that history suggests will be difficult to fulfill.

Healthy waters mean healthy wallets: From empty hotel rooms along the Panhandle's sugary sands to empty shrimpers' nests in Louisiana, there were endless examples of how much Gulf Coast economies depend on clean beaches, wetlands and waters.

"This is part of our culture, people have got to understand. We're part of the whole chain. We consume the food, out little kids are playing in the Gulf," said Marylee Orr, executive director of the Lower Mississippi Riverkeeper. "We absolutely have to learn from this."

Environmental groups are using the spill to press President Obama to follow through on a pledge to restore a Gulf Coast plagued before the spill by pollution, declining fish stocks and disappearing wetlands. Three of them - the Environmental Defense Fund, National Audubon Society and National Wildlife Federation - called for BP to pay a $5 billion "downpayment" to help restore the fast-shrinking Mississippi Delta.

"Every time we stop paying attention, this coast comes back and bites us," said Paul Kemp, vice president of Audubon's Louisiana Coastal Initiative.

A tin ear is no friend in a crisis: Even with his distinguished British accent, BP boss Tony Hayward couldn't get away with such gaffes as calling the Gulf oil disaster a "tiny" spill into a "very big ocean." Or griping that he, too, wanted the spill to end because "I want my life back." Or setting Facebook and Twitter ablaze by taking a Saturday off to attend a luxury yacht race around England's Isle of Wight to cheer on his own boat, "Bob."

It'll give him something to mull over during those long, dark nights at his new post - BP's digs in Russia.