Answer
When God revealed His plan to destroy the world with a flood, He first 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, ESV). Later, in Genesis 6:17, after instructing Noah to build the ark, He reveals that He will bring a flood on the earth: “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” (ESV).
The reason God instructed Noah to build the ark was to safeguard humans, other mammals, reptiles, and birds from the flood waters. Interestingly, fish (and other aquatic creatures) are not specifically mentioned in God’s decree regarding the flood. Most people assume that the flood had no adverse effect on fish. That thinking stems from two lines of thought: 1) aquatic creatures do not have “breath” (although they do respirate), and 2) fish live in water and so would be at home in a flood. However, fossil evidence tells a different story, revealing that aquatic creatures definitely suffered from the flood (www.case.edu.au/blogs/case-subscription-library/young-earth-creationism-geological-evidence-and-the-age-of-the-earth, accessed 1/8/25). In fact, most fish and sea creatures did not survive the flood.
Dr. John D. Morris of the Institute for Creation Research points out that “over 95 percent of all fossils are marine creatures. They died and are fossilized by the trillions. Many are buried in great fossil graveyards, tightly packed together, choked with sediments, buried before they had time to decay” (“Fish in the Flood,” Acts & Facts, 2011, 40 (5): 16). Of course, it is obvious that there were many survivors, as a myriad of marine and freshwater creatures exist today. So, how did those that survived manage to do so?
The Bible says that “on that day [of the flood] all the fountains of the great deep burst forth, and the windows of the heavens were opened” (Genesis 7:11, ESV). This describes, in few words, what is the most catastrophic event the earth has ever seen. Not only did rain begin to pour down on the earth in a 40-day deluge, but creationist scientists believe that tremendous seismic events accompanied the downpour. Specifically, they believe that “the great fountains of the earth” bursting forth entailed the upheaval of enormous subterranean reservoirs of water, cataclysmic tectonic plate shifts, and widespread volcanic activity. These geological events were so severe that they transformed the earth in many fundamental ways.
A reasonable question is often raised. If both salt water and fresh water existed before the flood, how did marine animals and freshwater animals survive the flood at all? The mixing of fresh and salt water would likely result in an aquatic environment inhospitable to most aquatic life. The waters of the flood would have contained too much salt for freshwater creatures and too little salt for marine creatures.
One explanation is that aquatic life could have survived the mixing of rain, river, and ocean waters if, prior to the flood, the ocean had little or no salinity. Working against this theory are the fossils of marine life—virtually identical to today’s saltwater-dependent creatures. The fossil record indicates that antediluvian seas were somewhat salty, although salinity levels were probably lower than what we see today because the salt had not had as much time to accumulate. Likewise, fossils of freshwater aquatic life—virtually identical to today’s freshwater-dependent creatures—indicate that freshwater environments also existed in the antediluvian world. To destroy those environments would be to destroy those creatures.
Another, more likely, possibility has to do with the tendency of certain bodies of water not to mix. The laws of physics dictate that waters with varying temperatures, salinity, or turbidity tend to remain separated into zones. For example, two bodies of water of different temperatures will not readily mix. The denser, colder water stays beneath the warmer water, separated by a transitional zone referred to as the thermocline.
A similar phenomenon occurs when salt water and fresh water meet. Even when the temperatures of both the salt water and fresh water are equal, the salt water (being denser due to its salt content) will settle below the less dense fresh water, separated by a transitional zone referred to as the halocline. Dr. Morris elaborates: “In the complex of events and conditions that made up the Flood, certainly there were pockets of fresh water at any one time. . . . It would be unlikely for any one area to retain such zones for very long during the tumult of the Flood, but on a worldwide scale, some such segregated zones would have existed at any given time” (ibid.). This would have potentially provided separate, survivable environments for both freshwater and marine creatures.
Dr. Morris goes on to point out that we cannot know the tolerance of pre-flood aquatic creatures for sediment, salt, and temperature. They may have been more adaptable to different environments than the animals we observe today. He also notes that it is possible that great amounts of flora, including trees, brush, etc., were dislodged from the continents. Many creationists believe this resulted in large, floating mats of intertwined vegetation. Underneath those mats the water would have been less turbulent, thereby helping prevent the blending of saltwater and freshwater areas.
There is one more possibility for consideration, namely, that the aquatic creatures may have survived because God supernaturally protected them. The Great Flood was a supernatural event, a miracle of global proportions. To insist on only naturalistic explanations for the survival of aquatic life is to ignore the power of God. That said, it can be argued that it is more likely that God allowed the natural processes and events discussed above to preserve water-dwelling creatures.
In Genesis 7:21–23, sea life is not included in the list of creatures that perished in the flood: “Every living thing that moved on land perished—birds, livestock, wild animals, all the creatures that swarm over the earth, and all mankind. Everything on dry land that had the breath of life in its nostrils died. Every living thing on the face of the earth was wiped out; people and animals and the creatures that move along the ground and the birds were wiped from the earth.” This does not mean that the flood had no effect on aquatic life. Great numbers of aquatic life died, but God saw to it that enough survived, apart from the ark, to perpetuate their various species.
