“living soul.” The Hebrew word “soul” is nephesh (#05315 נֶפֶשׁ), and in the Bible, nephesh often refers to the life force that animates humans and animals. It is also sometimes used of “individuals,” as it is here in Genesis 1:21, where “soul” (nephesh) refers to the individual animal and bird, which is why the text says God created “every living soul that moves.” Here, “soul” refers to the individual animals, which is why so many English versions translate nephesh as “creature” in Genesis 1:21. The “creature” is called a “soul” because it is animated by nephesh, soul. This is not well understood in the Christian world and it is often taught that animals do not have soul, but Genesis is clear that they do; they are animated by “soul” just as humans are, and when they die their life force, their “soul” is gone.
[For more information, see Appendix 7: “Usages of ‘Soul.’”]
“And God saw that it was good.” This is in contrast to many ancient mythologies in which the creatures that lived in the seas were against God or were in chaos.