Why haven't them dress up a scuba equipment and research that peeble.
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Because we only have the picture to go on.

From a scientific point of view....Its just as important to state what you think is is'nt, and say why. As well as to say what you think it might be. Giving at least one scientific reason
to back up your case.

I thought this could be an interesting exercise
to help us all digest that Xmas pudding.

So you believe it's an object? (that landed in the water) What about the cloud of smoke (angle and size) by the flash?
the end

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"You will never find a real Human being - Even in a mirror." ....Mike Kremer.