However, flying at 500 metres (1500 ft) or lower, the crew judged the slick not to be oil.
I would have thought that'd be obvious. Aviation Turbine fuel is clear, and an aircraft wouldn't carry anywhere near enough "oil" to make that slick.
Originally Posted by Capt Groper
The BBC pics of possible oil skick looks more like red tidal algee
or Coral Reef spawn...very similar colour.