The Deepwater Horizon Gusher, 2010
Deepwater Horizon rig

On April 21, 2010, the Deepwater Horizon rig exploded, starting a months-long gush of oil into the Gulf.

U.S. Coast Guard via Getty Images

The controversy surrounding deep-water drilling, exemplified by BP's Deepwater Horizon rig in the Gulf of Mexico, quickly validated the naysayers when, on April 20, 2010, it exploded and sank, killing 11 of the workers on the platform.

And that was just the beginning. With the sinking of the platform, the pipe carrying oil up from the sea floor failed, and oil began gushing into the Gulf at an alarming rate. The flow was captured by live video feed, and people all over the world watched in horror as an eventual 5 million barrels of oil rushed out in the largest oil spill ever.

As it turns out, there is no easy way to fix a faulty pipe about a mile below the surface.

What followed was a series of failed attempts to stop the stunning flow of oil that threatened the ecology of the Gulf and the livelihoods revolving around it. There were multiple "last-ditch" attempts: the "Top Kill," which pumped drilling mud into the pipe to try to clog it; the "Junk Shot," which sent trash into the pipe with the same goal; and the "Top Hat," which tried to cap the pipe using underwater robots.

It was the last of these Top Hats that finally worked. This one had a tighter fit, and on July 15, oil stopped flowing into Gulf waters for the first time in more than three months. According to BP, those operations ran the company about $3.5 billion -- with more clean-up costs to come.

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