There's a bigger problem then that. To cover Everest would require between 200~400% more water then exists on Earth. If it came from within the Earth, it would be superheated, its release would kill everything except thermophilic bacteria. If it came from a comet, well the size of such a comet would end all life. If it rained, the heat from that much precipitation, much less the toxicity would kill all complex life as well.
What's the point in discussing how they lived after when the flood itself results in mass extinctions of virtually all life on the planet?