Question: "Were fish and sea creatures also destroyed during the Flood (Genesis 6-8)?"
Answer: When God revealed His plan to destroy the world with a Flood, He told Noah, “I will blot out man whom I have created from the face of the land, man and animals and creeping things and birds of the heavens, for I am sorry that I have made them” (Genesis 6:7). Interestingly, fish and sea creatures were not mentioned.
Several passages in the Flood section of Genesis help shed some light on the question of whether or not fish were killed in the Flood. Genesis 6:17 states, “For behold, I will bring a flood of waters upon the earth to destroy all flesh in which is the breath of life under heaven. Everything that is on the earth shall die.” Specifically, everything on the earth would die. The flood of water would drown them. Logically, animals that live in the water would not be affected by more water. Also, it is hard to see how fish could be described as having “breath.”
Land animals and birds were selected to board the ark, but fish and sea creatures were not (Genesis 6:19-21; 7:2-4). This would seem to indicate that sea creatures did not need the ark in order to survive.
Genesis 7:20-23 lists animals that died, but sea life is not included: “The waters prevailed above the mountains, covering them fifteen cubits deep. And all flesh died that moved on the earth, birds, livestock, beasts, all swarming creatures that swarm on the earth, and all mankind. Everything on the dry land in whose nostrils was the breath of life died. He blotted out every living thing that was on the face of the ground, man and animals and creeping things and birds of the heavens.” The reference to “dry land” limits what types of animals were affected.
After the Flood, “God remembered Noah and all the beasts and all the livestock that were with him in the ark” (Genesis 8:1). Why didn’t God “remember” the fish and sea creatures? They had not been destroyed like the other animals.
It is interesting to observe how the Hebrew worldview categorized animal life. The fifth day of creation included the creation of fish and sea life as well as flying creatures and birds: “So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good” (Genesis 1:21). Land animals were created on the sixth day (Genesis 1:24). Based on these verses, the Jewish people saw animal life in three categories—sea life, flying animals, and land animals. Of those three categories, only the flying animals and land animals were taken aboard the ark. The fish and sea life were not at risk under the water.