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

We still breathe water. The oxygen from air first dissolves into the water layer covering our lungs. It is from that water that the oxygen then moves into our bodies.