New Defender's Study Bible Notes
104:6 with the deep. The completed earth was later once again covered with water at the time of the great Flood when the waters rose above all the mountains (Genesis 7:19,20) of the antediluvian world.
104:7 they fled. God intervened to end the Flood (Genesis 8:1). The words “fled” and “hasted” indicate very rapid drainage, implying much geological work being done.
104:8 down by the valleys. The sense of this statement is: “The mountains rise; the basins sink down.” This post-diluvian mountain-building epoch permitted the Flood waters to drain off into the new ocean basins.