17 Now the flood was on the earth forty days. The waters increased and lifted up the ark, and it rose high above the earth.
18 The waters prevailed and greatly increased on the earth, and the ark moved about on the surface of the waters.
19 And the waters prevailed exceedingly on the earth, and all the high hills under the whole heaven were covered.
20 The waters prevailed fifteen cubits upward, and the mountains were covered.
21 And all flesh died that moved on the earth: birds and cattle and beasts and every creeping thing that creeps on the earth, and every man.
22 All in whose nostrils was the breath of the spirit of life, all that was on the dry land, died.
23 So He destroyed all living things which were on the face of the ground: both man and cattle, creeping thing and bird of the air. They were destroyed from the earth. Only Noah and those who were with him in the ark remained alive.
24 And the waters prevailed on the earth one hundred and fifty days.
Noah illustrates the Scripture terms “lost” and “saved.” Standing without the door of the ark he was lost, that is, exposed to the coming judgment and sure to perish. Standing inside the door he was saved, that is, sheltered from the coming doom and sure not to perish. To pass from the one condition to the other he had but to take one step—a step into the ark—and he was in immediate safety.
Noah was saved through the baptism of the ark. The ark was sinless, Noah sinful, the ark suffered the fierceness of Divine anger—a baptism into death—but not one wave of that judgment reached Noah. He was absolutely safe. Noah could not perish because the ark could not perish. The ark could not perish because Jehovah was in the ark; that ark was Christ—God in Christ reconciling man unto Himself. He did not say “go into the ark” but “come into the Ark.” The apostle Peter in the third chapter of his first epistle points out that this is how sinners are saved—the baptism into death and the resurrection out of death of Jesus Christ. He says that the baptism and resurrection of the ark was a type of the death and resurrection of Christ; and declares that that antitype-baptism saves believers. — Williams, pages 13-14.
All the high hills under the whole heaven were covered (v.19) — eliminating all arguments that the flood was local.
The word prevailed appears four times in this passage (vs. 18, 19, 20, and 24). It means literally “were overwhelmingly mighty.”
It is instructive to note what did not die. Animals that were not nephesh did not die. Nephesh animals are those with their life-blood in them — i.e., flesh. Animals that do not breath through nostrils into lungs did not die. This includes insects. The Bible is clear that they must have survived. We can only surmise how, though many have suggested that they could have lodged in vegetation mats.
Amphibians, also, though having lungs, could have survived the Flood, as they absorb oxygen through their skin. Certainly amphibian larvae would survive as easily as fish.
Finally, even nephesh life that breaths through its nostrils would survive if it was not included in “all that was on the dry land.” So whales, dolphins, and other marine mammals, and, possibly, marine reptiles … would survive. — Taylor, pages 162-163
The divinely superintended order within the Flood event—and the adept literary retention and enhancement of that order by the writer—is further borne out by the various periods of days that are mentioned throughout the course of this and the following sections—to wit: seven days of waiting (7:10), forty days of rain after the door of the ark is “closed” (7:12, 17), one hundred and fifty days of the water “prevailing” (7:24), one hundred and fifty days of the water “subsiding” (8:3), forty days before the window of the ark is “opened” (8:6), and seven days of waiting before the dove is sent out the second time (8:10). These periods thus mirror the overall structure of the Flood narrative by forming a “mini”-chiasm/inversion that serves to further reinforce the “movement” of the narrative, both physically and theologically, as the waters of the Flood—and God’s judgment of man—rises, peaks, and subsides. — Wechsler, pages 145-146.