Bursting dams cause trees to be swept away and often slime the entire flood zone with killer mud as pictured here in Brazil. The
worst tsunami on record ran up to 1,720 feet in Lituya Bay, Alaska. The
force of that wave removed all trees and vegetation from that elevation
down to sea level. Likewise,
if floodwaters rushed onto the faces of the continents and settled
30,000 feet deep before rushing off again, the
entire face of the planet would have been scrubbed bare of vegetation by cataclysmic
erosion. The Bible doesn't say that Noah saved plants. So, how have circa 400,000 species of plants survived to this day? And, if God saved with a wave of His hand and preserved them miraculously, why didn't He do that for the animals and spare Noah the nightmare of gathering, loading, feeding, doctoring, unloading, and dispersing them?
For most saltwater plants, the drop in salinity would have killed them. And, for most freshwater plants, the increase in salinity would have killed them. And, for most land plants, months of submersion in any kind of liquid would have killed them. So, there is no conceivable natural scenario in which a sufficient variety of seeds could have survived on floating debris mats, in the gullets of birds, in animal fur, in the wind, or in the Ark's food stores that would explain the diversity of plant life that currently covers the planet. The only possibility is that God collected all the seeds for Noah so he could save them and then planted them for Noah across the globe after the flood receded.
Could seaside species such as mangroves have survived for months of submersion in saltwater? Not at that depth! If water covered Mount Everest, the pressures at the depth of the usual coastlines would be about 1,000 times greater than normal, crushing the life out of plant structures. Marine creatures pose the same problems for Noah. To survive, they would have needed a miracle to adapt to changes in aquatic salinity. And, they would have had to cram their bellies full of food and swam upward as the waters rose to stay in the habitable pressure ranges. There is no record of Noah gathering fish and keeping all the varieties in tanks at the proper pressures and temperatures. There is no biblical hint that Noah even lived by the lakes, rivers, and oceans where he could haul in the fish that needed saving. Perhaps his flood was local.