In an oxygen-rich regime, they would almost certainly be impossible. Such a mass of water as the flood would have provided sufficient buoyancy to float the polar caps off their beds. Since most coral are found in shallow water, the turbidity created by the runoff from the land would effectively cut them off from the sun. Some require cool clear water, some need brackish water, some need ocean water, some need water even saltier. A flood would have destroyed at least some of these habitats.
Fossil pollen is one of the more important indicators of different levels of strata.
Each plant has different and distinct pollen, and, by telling which plants produced the fossil pollen, it is easy to see what the climate was like in different strata. The moon is slowly sapping the earth's rotational energy. The earth should have rotated more quickly in the distant past, meaning that a day would have been less than 24 hours, and there would have been more days per year. Devonian corals, for example, show nearly 400 days per year. As pseudoscientists, creationists dare not test this major hypothesis that all of the fossilized animals died in the Flood.