Where is it all?
Most of the oil has evaporated or dissolved, but up to 10 million gallons remain on the sea floor, and gobs of oil can still be found nestled into marshes along the coast.
A study by Mandy Joye, an oceanologist at the University of Georgia, claims that oil is scattered over 1,200 square miles of sea floor. BP disputes those findings, and says that all of the oil is "accounted for".
What was the impact on wildlife?
The immediate impacts were severe, with oil-soaked birds, fish, and turtles washing up on shore along the coast.
However, rebounding wildlife populations indicate that the long-term outlook may not be as bad as was originally feared .
A report released by BP claims that there is no evidence of any "significant long-term population-level impact to any species", though scientists have cautioned that the full scope of the impact will not be known for some time.
What about the dolphin deaths and fall in sea turtle populations?
Bottlenose dolphins in the gulf have been dying at more than twice the normal rate over the past five years. In 2011 alone, a record 335 died.
Stephanie Venn-Watson, a veterinary epidemiologist at the Marine Mammal Foundation, told the Associated Press that the rise in deaths "matched the timing, location and magnitude of the oil spill."
Similarly, the nesting habits of the endangered Kemp's Ridley sea turtle changed dramatically around the time of the spill.
No link between the spill and the declines in dolphin and turtle populations has been scientifically proved.
BP's report notes that the dolphin mortality rate was already elevated prior to the spill, and that "natural variability and record cold temperatures" could explain the variations in turtle nesting habits.