I dont know if it was said, among the other completely obvious problems that we all ignored there is one more.
What ever water was in the "atmosphere" would raise atmospheric pressure.
i.e. if there were say 100 ft of rainwater to cover the earth over our heads, the atmospheric pressure would be the same as it would be 100 ft under the sea.
Creatures above the sea are built to take 15psi, not any more.