By the same token the majority of life in freshwater lakes ,rivers and streams would not survive in salt water.Smiddy, you forget that the flood, (just like the future reverting back to paradise) was a time of monumental change. (the pyramids were build at the same time);--after the flood, of all universal, total herbivores, some became meat eaters, so who says the metabolisms in the water creatures were not changed at the same time? after all,
talking too was taken from snakes, and bestowed on donkeys or asses. may be the pre-deluge waters in the heavens had all these phase changing qualities?