What did God create on the fifth day?

Answer 1

In short, the fish and birds.

(Genesis 1:20-23)

20 Then God said, "Let the waters swarm with fish and other life. Let the skies be filled with birds of every kind." 21 So God created great sea creatures and every living thing that scurries and swarms in the water, and every sort of bird-each producing offspring of the same kind. And God saw that it was good. 22 Then God blessed them, saying, "Be fruitful and multiply. Let the fish fill the seas, and let the birds multiply on the earth."

23 And evening passed and morning came, marking the fifth day.

Answer 2

The fifth day Creation, of this earth age (eon) is defined in the book of Genesis 1:20-22. There you discover all aquatic (sea, ocean, water) life forms were created, along with all the fowl (birds) life forms that fly. Remember that in 2nd Peter chapter 3 you are told that a day with the Lord is 1000 years, therefore the fifth day was 1000 years long, not 24 hours as some incorrectly assume. You need to go read Genesis chapter 1 for yourself to understand all that is written there.
The birds and fish, I think.

Answer 2

Day by day, God created the universe and its contents (Genesis ch.1).God created the universe out of nothing (Exodus 20:11, Isaiah 40:28; Rashi commentary to Genesis 1:14; Maimonides' "Guide," 2:30).Note that the Torah, in describing the Creation, deliberately employs brevity and ellipsis, just as it does in many other topics. See the Talmud, Hagigah 11b.

• On day 1: God created the universe in general, light, and this Earth. The light was not the same as that of the sun. Rather, it was light that God created before the sun, and which emanated from a point in space without any physical source; like what we might term a "white hole."
  
• On day 2: God created the separation between the Earth and the upper atmosphere.
  
• On day 3: God separated the continents from the oceans, and created plants.
  
• On day 4: God created the sun, moon, and stars.
  
• On day 5: God created birds and fish.
  
• On day 6: God created animals and people.
  
• On day 7: God ceased creating, thereby creating the concept of rest.
  

See also:

Is there evidence for Creation?

Can you show that God exists?

Seeing God's wisdom

Answer 3

God created the birds and all the living creatures in the sea's and oceans on the fifth day.