On the fifth day God created the creatures that live in the sea and the birds of the air. Read it for yourself in Genesis 1:20-23. You may select your favorite version of the Bible, or better yet read it in more than one version for fuller understanding.
God created the fish and other kinds of life found in the sea. Here are a few videos I found to show the diversity found in our oceans. Some were developed with political intentions, so it may not suit your purposes to use them with children.
http://ocean.si.edu/ocean-videos/sea-creatures-deep-video-national-geographic-and-census-marine-life (Deepest ocean creatures)
I believe it is worth noting that one of the sea creatures named in the Bible was the leviathan. You can learn more about this terrifying creature by reading Job 41. The leviathan could easily be one of the dinosaurs and it is evidence that dinosaurs, and man did co-exist before the dinosaurs became extinct. Many want to diminish this animal as if it were a crocodile, but no crocodile fits the description given in the later verses. The pictures that the orientals paint of dragons more readily fit the description given in Job 41.
Not only did God create the creatures in the seas on this day, he also created the birds. Now that there were trees where the birds could build their nests and other plants they could perch on, God was ready to create the birds. What beauty he brought into the world when he created them. The Cornell Lab of Ornithology at Cornell University offers a fantastic website that teaches us many things about the birds. Spend time exploring it, especially their Bird Guide and learn more about God’s handiwork.
In Matthew 6:26, Jesus used the birds as an example of how God takes care of the birds and he will also take care of us.
Stand in awe of God’s creation and know that he is the One who is supreme then and now.
The Creation, a Bible storybook for children by Janice D. Green