All
I have to say that in my first several viewings of the Cook Photo, I could not see the similarity to a wheel or engine cowling at all, rather just a bunch of coral.
At some point, my brain flipped the components around like one of those optical illusion graphics that can be seen two ways and all of a sudden I got it. Just like many of those optical illusions, once you see it one way or the other, it becomes really hard to see it the way one originally saw the objects, and now when I look at the photo my brain only shows me the version that has a circular object. I have to really work to get back to my original inverse view, but I can and it still shows me a bunch of coral.
I think we need to be a bit cautious about assuming that what we think and want to see in this photo is actually there. I think our collective brains are playing tricks on us. In any case, this photo is certainly not definitive proof of Amelia's aircraft.
As one of the few who has actually been diving on this reef, my best guess is that we're looking at coral that due to the composition of the photo is providing an optical illusion of circularity and man made-ness. The scale is off for the object to be an engine.
I'm also not surprised that they were unable to find it again when they went back, particularly if it is only coral. I would think that an engine would be far harder, but not impossible to miss.
Just my 2ยข
Andrew