Charles Spurgeon Commentary Genesis 1:20-23

"And God said, Let the waters swarm with swarms of living creatures, and let birds fly above the earth in the open firmament of heaven. And God created the great sea-monsters, and every living creature that moveth, wherewith the waters swarmed, after their kind, and every winged bird after its kind: and God saw that it was good. And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let birds multiply on the earth. And there was evening and there was morning, a fifth day." — Genesis 1:20-23 (ASV)

There was no life in the sea or on the land until all was ready for it. God would not make a creature to be unhappy. There must be suitable food to feed upon, and the sun and moon to cheer and comfort before a single bird could chirp in the thicket or a solitary trout could leap in the stream.

So, after God has given people light and blessed them in various ways, their spiritual life begins to develop to the glory of God. We have thoughts that soar like fowl in the open firmament of heaven, and other thoughts that dive into the mysteries of God, as fish dive in the sea. These are later developments, subsequent growths from that same power which at first said, Let there be light.