Eli5: How was the first ancient animal to ever step (foot?) out of the water, able to survive breathing air instead of water?

Question

Eli5: How was the first ancient animal to ever step (foot?) out of the water, able to survive breathing air instead of water?

In: Biology

Answer 1

It didn’t happen overnight. There are plenty of creatures today that live in the interface between water and air and spend the time in either that suits their capabilities and needs.