Was the ground muddy? I admit some fish have sturdy fins while others do not. And it depends on the shape of the fishes body. A fish that's more of a flat body well fall on its side while something like a catfish can land on its belly and slither. The mud or dirt will determine it's ability to move on land. Fish adapt to their environments but they will never grow legs. A monkey will always live in trees. Apes will always live in jungle environments and be hyper aggressive when feeling threatened or challenged otherwise they will be reclusive. Humans will always live where ever they please doing as they please acting as they please. They will adapt to cold or warm climates. Most changes are insignificant like adaption to climate. People did not come from apes. In the beginning God created the heavens and the earth. Look down a bit and it says God created fish, God created birds, God created trees and grass and fruits, God created cattle and creatures that crawl and beats of the earth, all mating with their own kind then God created humans, a special creation made from dust with the breath of life breathed into them.