Furthermore, according to your "theory" all of the large creatures should be found in the upper rock layers and all of the smaller ones in the lower rock layers. We have found ape-like fossils in relatively shallow layers and various dinosaur fossils in lower layers. Aren't dinosaurs larger than apes?
On the contrary. Present experience in viewing the status quo testifies that the larger and smaller things can be juxtaposed WRT the law of gravity depending on the environment. As far as I know the world has never demonstrated bigger things always to be higher and smaller things lower. It's not as though the Law of Gravity has been the only operative factor in history.
And where did the Law of Gravity come from anyway? Do you think if we all put our intelligent heads together we could come up with something as nifty and set it rolling throughout the rest of history?
Anyway, given an aquatic phenomenon of catastrophic magnitude there would probably be anomalies. No surprise there. Do you know of any such phenomenon that has been documented by human voice and hand throughout recorded human history? The fossil record agrees quite well with the proposition of a great flood. Why would anyone fabricate such a story out of whole cloth?
The largest dinosaurs were far bigger than elephants, much less apes, but there were many smaller dinos, some of them quite petite. All the dinosaurs of all sizes fall within a certain range in the geologic column, layers which correspond to a time range of 230 to 65 million years ago.
Below them are trilobites, many of which are no bigger or denser than modern pillbugs. The pillbugs are up here and still alive, the trilobites are down there and long gone, and in between are the dinosaurs of all sizes, also long gone. The uppermost trilobites are always far below the lowermost dinosaurs. Never an overlap. The dinosaurs never overlap with humans, apes, elephants ...
The only kind of "sort" in the column is from a few, simple ancient forms toward (overall) increasing complexity and diversity. There was long a trend toward increasing size as well but that seems to have passed a peak.