As with poly, I am not totally clear what you mean.
I am guessing a reference to "the flood".
There is no simple answer, unless it is to say, "Well,
you cant be looking for fossils underwater.
If you drill an oil well in Kansas, you will get little
pieces of seashells, from hundreds of feet underground.
Yeah, the water has long since receded from Kansas.
Those are marine fossils, of cretaceous age. There
was an inland sea, with giant sea turtles nesting on
the beach in Wyoming, 60 ft crocodiles lurking about.
That sea is long since gone, that which got
buried in sand or mud got fossilized, and
most of the life disappeared with no
trace. A typical setting for fossils to form would
be in a shallow bay,or in a river delta where
sediments will be brought in and sink to the
bottom.
Since our fossil of a sea dragon (Mososaur)
was buried 70 million years ago or so,
the rocky mountains started rising and eroding
so that a vast sediment plume spread out
across the prairie and buried the old seafloor.
Historical geology is actually pretty interesting.
The landscape really comes alive if you
have even a little understanding of what
you are looking at. The landscape can be
read, but you have to know how to read!