A year after the worst oil spill in American history, it is difficult to assess the long-term environmental damage.
Nearly five million barrels leaked into the Gulf of Mexico after a BP rig exploded, killing 11 workers, threatening the coastline of four states and thousands of livelihoods.
Some scientists say the scene underwater now gives grounds for optimism.
Dr Quenton Dokken, whose Gulf of Mexico Foundation works with government agencies and is partly funded by oil companies, took part in a dive to examine a rig.
“There was absolutely no evidence, visual evidence (that) these platforms, these artificial reefs had ever been in the proximity of a major spill,” he said.
Another expert who studied underwater images did see evidence of damage.
“I didn’t see any larger fish except maybe one in the videos,” said Dr Paul Sammarco from the Louisiana University Marine Consortium. “What I was seeing was a lot of small fish, which of course make it look vibrant, and that’s good. But it’s looking as though the older, larger fish that make up the larger population, the resident population, weren’t there.”
Other scientists say it is too early to make a long-term judgment and data is still too sketchy. There are claims that evidence is being kept from the public domain because of ongoing litigation.