Ramban, on Gen 7:23

“And he destroyed all the substance that was upon the earth, from man even to beast, and the creeping things and fowls of the air: and they were destroyed from the earth: and Noe only remained, and they that were with him in the ark.”

“AND HE BLOTTED OUT EVERY LIVING SUBSTANCE WHICH WAS UPON THE FACE OF THE EARTH. After having said, And all flesh perished, and having said, whatever was in the dry land, died, Scripture continues to say, And He blotted out, meaning that the bodies dissolved and became water, just as is in the verse, And he shall blot them out in the water of bitterness — for the waters of the flood were hot, as our Rabbis have said. But if so, the fish also would have died. Perhaps it was as the Rabbis have said in Bereshith Rabbah: “Whatever was in the dry land died, but not the fish in the sea. And some authorities say that they too were destined to be destroyed, but they fled to the Mediterranean.” (ocean), but usually meaning the Mediterranean Sea. (See Jastrow.) Either way the fish were saved. Both of these opinions are plausible. For it is conceivable that the hot waters of the flood mingled with the seas, heating only their upper waters, while the fish descended to the depths of the ponds and lived there. Or, in accordance with the opinion of some authorities, it is possible that the fish in the waters of the countries near the Mediterranean (ocean), but usually meaning the Mediterranean Sea. (See Jastrow.) fled there when they felt the heat of the water, and were thus saved. And even if all those outside the Mediterranean died, since the majority of fish are in the Mediterranean (ocean), but usually meaning the Mediterranean Sea. (See Jastrow.) where the waters of the flood did not come down — as it is said, And the rain was upon the earth — the fish were thus saved. For none of the fish were brought into the ark to keep their seed alive, and at the time of the covenant it is said, I establish My covenant with you… and with every living creature that is with you, the fowl, and cattle, and every beast of the earth with you; of all that go out of the ark, but it does not mention the fish of the sea. AND THEY WERE BLOTTED OUT FROM THE EARTH. The commentators have explained that the reason for the double [expression, And He blotted out … and they were blotted out], is that their remembrance was forgotten since they had no seed. But what need is there to say that after we are told that they all died? Perhaps on account of the fowl and some creeping things, Scripture tells that none of their eggs were left on any tree or under the earth for everything was blotted out. It is probable that the sense of the verse is as follows: “And He blotted out every living substance which was upon the face of the earth, for from man to beast to creeping things and to fowl of the heaven, they were blotted out from the earth, only Noah remaining alive.” Now our Rabbis have expounded: “And He blotted out, meaning from this world. And they were blotted out from the earth, meaning from the World to Come.” The Rabbis thus explained “the earth” mentioned here as meaning “the land of eternal life.” I have already alluded to its secret.”

Imported from an open dataset — not yet checked against the printed edition.