Symmetric decon is wonderful the way it preserves polarity,
but it has one feature that is really embarassing.
About 150ms after the air gun blast is a bubble collapse blast.
At early times they are quite different in frequency content and size,
but because the bubble contains mostly the lower frequencies,
its relative contribution becomes much stronger later in the record.
What symmetric decon does with this bubble is horrifying.
It gives a precursor 150ms before the water bottom.
And also before every other event!