The oil leaked from the Big Spill in the Gulf of Mexico, in 2010, spread below the surface much farther than was visible on the surface from satellites.

Since fishing was not banned in areas beyond the visible oil slick, that underwater oil could have got into fish which humans then ate.

I wonder if the dispersants that BP poured on the oil, which make the oil mix more with water, played a role in causing that. This response was criticized at the time.