The Darby Translation is the most accurate, word-for-word translation of these verses. First note that the word "creatures" is the Hebrew word, nephesh, (H5314), and it means soul. Genesis 1:20-23 (DBY), 20 And God said, Let the waters swarm with swarms of living souls, and let fowl fly above the earth in the expanse of the heavens. 21 And God created the great sea monsters, and every living soul that moves with which the waters swarm, after their kind, and every winged fowl after its kind. And God saw that it was good. 22 And God blessed them, saying, Be fruitful and multiply, and fill the waters in the seas, and let fowl multiply on the earth. 23 And there was evening, and there was morning — a fifth day."
In Genesis 2:7, God created Adam (Darby Translation), "And Jehovah Elohim formed Man, dust of the ground, and breathed into his nostrils the breath of life; and Man became a living soul (nephesh)." In the Hebrew, all animals are souls.
Also in verse 21, the King James Version of the Bible reads "God created great whales." That's a poor translation. This is Strong's word, (H8565), tanniyn, and it means "a marine or land monster." The Hebrew word for "great" precedes tanniyn, so "great sea monsters" is a good translation. What were those creatures? Sea dinosaurs and winged dinosaurs.