As previous contributors have already stated the length of the narrow 'leg' of the spill in the AF447 case does not fit to fuel rising from the bottom.
It is much too short and narrow for that.
But we should consider that an Airliner which crashes usually doesn't come to a full stop immediately.
the dirction of the narrow 'leg' of the spill roughly matches the flight path which AF447 would have to be taking in order to arrive where the spot was found.
So a possible scenario trying to explain the shape of the spill could be a first (severe) impact releasing a big amount of fuel where the bigger oval part of the spill was seen followed by continued travel of the wreckage for a couple of hundred meters to the SE. Than sinking of the wreckage continuously releasing decreasing amounts of fuel. Sinking and resurfacing of the remaining fuel could take a couple of hours, roughly matching the 1300m length of that 'leg'.
Just a desperate attempt to match the finding (spill) to the assumed cause (AF447 impact).
Generally I'm not really that convinced anymore ithat the spill was really linked to the crash. On the other hand: Where there any ships around at that time (+/- 1 or 2 days) that could have caused the spill?
Did anyone check in Vesseltracker or similar?