The self-existent, maker of heaven and earth, has divided light from darkness and dividing surface water from water vapor in the clouds. He caused the dry land to appear and on the same day created life. The 4th creation day brought forth the sun moon and stars giving us regular seasons, tides, and the ability to track them by watching the heavens, but still no animal life on the earth.
20 Then God said, "Let the waters abound with an abundance of living creatures, and let birds fly above the earth across the face of the firmament of the heavens."
If you wonder about the order of creation why the 4th day was about the heavens and not new forms of life on earth, the answer is most likely oxygen. Evidence shows the earth had very little oxygen when the land first appeared, but the autotrophic life of day three began to fill the great oxygen sinks of the ocean. Scientist say the over 2 billion years ago a great oxygenation event occurred where the oceans became saturated with dissolved oxygen setting the stage for a new kind of life, essentially anything that swims or flies.
That word "abound" in other Bible translations is "team" or "swarm". Anyone who has been near the ocean has observed this teaming, swarming or schooling of fish and other aquatic life. Fishermen look for these great schools of fish. Some professional tuna fishermen use planes to spot dark patches on the water as those are schools of bait fish because they know the larger game fish like tuna will find the large schools of bait fish. My best day fishing ever was with my Dad and my Uncle off Galveston Island. We found a swarm of brown gulf shrimp, and a large school of gulf trout found them to. All you had to do is put a shrimp on your hook and throw it in and a gulf trout would jump on it.
This same behavior is why fishermen can use nets to catch great numbers of fish. The Gospels of Matthew and Mark both record that four of Jesus disciples were two sets of brothers, fishermen by trade, and they were hard at work when Jesus called them to leave their nets and become Christ followers. Jesus was calling them first to learn, then to help and finally to teach and preach.
Later in Luke chapter 5 Jesus has Simon Peter use a boat as a floating platform from which Jesus can teach, then when Jesus is done he rewards them with a quick catch of a great school of fish.
21 So God created great sea creatures and every living thing that moves, with which the waters abounded, according to their kind, and every winged bird according to its kind. And God saw that it was good.
In addition to the smaller schooling fish, God also made some bigger ones. The Hebrew word for sea creature is "tanniyn" which is translated as whale, dragon, serpent, some translations even say sea monster. So "sea creature" is probably as good of a translation as we can get. I can't tell you exactly what they are, but I know they were big.
Verse 21 also reemphasizes that these animals abounded or reproduced according to its kind. If you remember our study of the 3rd creation day we had this same language used for plant life. The Hebrew word translated kind is "miyn" which means to portion out. In terms of DNA this a means fish will always produce another fish, a bird will always produce another bird, and a crab can't produce anything other than another crab. Of course we know this conflicts with current evolutionary theory. Some say that this fifth creation day corresponds with an event known as the Cambrian explosion which was known to Charles Darwin when he made his theory, and he felt that the Cambrian fossils represented a great challenge to his theory, but he hoped it was just a puzzle that science could later solve, but it still hasn't happened.
Cambria is an ancient term for Wales, a part of Great Brittan where this geological period or rock layer was first discovered. But the greatest collection of fossils from this period was actually found in British Columbia. What these fossils show is the sudden emergence of practically every known phenotype of aquatic life. Fish, crabs, clams, worms are all found for the first time in this one rock layer. While the evolutionary story is one of slow random change over time, this fossil record is more consistent with massive waves of creation like those found in Genesis.
What do scientists say when the evidence doesn't match their theory? Well the evidence is wrong of course. First they say the fossil record is incomplete, this is their favorite defense for the untold millions of transitional species which had to exist according evolutionary theory, but are almost never found in the fossil record. Now everyone agrees that fossilization is an unusual event, most things that die don't make a fossil. But the more animals you have a more likely it is that one will make a fossil. So pay attention again to this idea of swarming ocean life, if all of these creatures existed before this time in earlier transitional form, then they would likely make a fossil, but sudden appearance, not slow evolution is still what the evidence shows.
Others have suggested that there are conditions under which rapid evolution is possible, but again this is theory without evidence. Chaining together millions of positive mutations to make more advanced creatures, is the story, but what geneticist find in the lab when studying mutations just doesn't agree with the story. Starting in the 1980's with Japanese geneticist Motoo Kimura there has been a growing tension between geneticist and old school evolutionist because the statistical reality of genetic studies still don't support the requirements of the evolutionary time line. We will have more to say about this in regard to the 6th creation day. This era of the fossil record is so important to earth's history some even refer to it as the "Biological Big Bang". All forms of sea life made all at once, is the claim made by the Bible and it is substantially verified by nature in the fossil record. In the words of former Oxford Zoologist and current atheistic author Richard Dawkins: "It is as though they were just planted there, without any evolutionary history."
For anyone interested in a comprehensive essay on the theories and challenges of the Cambrian explosion I recommend a paper by Microbiologist Stephen C. Meyer, along with P. A. Nelson, and Paul Chien : "The Cambrian Explosion: Biology's Big Bang" http://www.discovery.org/articleFiles/PDFs/Cambrian.pdf
While the sea creatures of Genesis 1 are well documented as fossils, the birds are not. Given the vast numbers and diversity of birds we see today their poor representation in the fossil record is curious. But that answer is pretty simple and very logical when you consider the distinctive quality of birds specifically that they fly as verse 20 points out. What that means is that birds have a unique design among the animals of the earth. Because they have to be lightweight in order to fly their bones are mostly hollow, as you might imagine this bad news if you want a bird fossil, as they decompose very quickly. This also points out the silliness of the Jurassic Park theory that great dinosaurs became birds. As they would have to evolve hollow bones long before they could fly, that adaptation would be disastrous for any land animals trying to survive this slow evolutionary change.
23 So the evening and the morning were the fifth day.
"yo·vm cha·mi·shi" like the creation days before it brings strong evidence for supernatural creation. Each day draws a sharp contrast between what nature can do with the sustaining and adaptive features God has given it, versus the supernatural action of the Creator unmeasured in intellect and power. Scientists look at the Cambrian rocks and wonder at the sudden explosion of life revealed there. Creationist look at the same evidence see the tremendous correspondence with the Genesis 1 revelation which has the same supernatural Author as the birds and fish of the 5th creation day.
We should remember as we dig into the details of each creation day that they all begin with the same phrase "vai·yo·mer e·lo·him" – Then God said. The things we see in nature are not only what God made, but the way he chose to reveal himself to the people he will make on the 6th creation day.
When we look at the heavens we see planets with too little atmosphere and no water, planets with too much atmosphere and thus no light and still no water. We see planets with no permanent rocky surface and no plant life. Some planets orbit the wrong kind of star or one in an unstable part of its life, or simply orbit at the wrong distance. Most planets don't have a sun or moon like ours, and most reside in the wrong part of their respective galaxies. All of these things support the rare earth hypothesis, and match the expectations of Biblical creation.
We know of no other place in the Cosmos where God had intervened in such remarkable and frankly obvious ways to reveal himself to us. Why things are the way they are, is a question that will always lead anyone unavoidably to the reality of God, and supernatural creation. Natural science or natural philosophy as it was formally known, does a pretty good job answering "how" questions but it is totally unequipped to tell you why.