Hi VM: Like some others, I developed an exhaustive post on the Flood, most of which was posted on H20. In that series, I discussed fresh water fish, and some additinal complications.
1. The minimum level to cover the tops of the highests mountains would have been about 30,000 feet deep if one uses Mt. Everest at 29,000+ feet. The intense water pressure near the ground's surface would have forced most sea-life species up closer to the water's surface, thus causing serious problems with the food supply, especially since the flood lasted for months.
2. Presuming that much of the rainfall and artesian wells would have been fresh water, this would have greatly diluted the oceans salt content, creating yet another problem for salt water species as well.
There are many other logistical problems associated with the notion of a global flood, but just the above alone shows the serious problems with the concept.
Fundamentalists and Apocalyptics will argue every problem away by either using plausibilities, or when out of ideas, will resort to God's magic hand to protect every problematic situation. But, in doing this they are also forced to admit that the geological evidence resulting from such a global flood 3,500 years ago would also have to be altered by God's magic hand to create new evidence that fools scientist today into believing that a global flood is not possible; thus making God a liar by use of deception.
These young-earth global-flood people could easily solve the problem by admiting that the flood was a local event, and move on. But they are stuck in the rut of trying to prove a claim that is not only unprovable, but that facts in evidence prove otherwise. - Amazing