New Defender's Study Bible Notes
1:10 Seas. As the solid materials precipitated and then moved down and around under the forces of gravity, internal heat, and other electro-magnetic energies (not to mention the outflowing energy of the divine Word), great basins opened up to receive and store the waters. Some of these waters were trapped and stored in the “great deep” (Genesis 7:11), subterranean chambers beneath the earth’s crust. Others accumulated in surface basins. However, all were evidently interconnected through a network of subterranean channels, so that they were both singular and plural–gathered together into “one place,” yet called “Seas.”
Thus were established the primeval continents and primeval oceans. We do not now know the original geography, however, since all was cataclysmically changed at the time of the great Flood. We can infer that the topography was gently rolling and the waterways were relatively shallow and narrow, since all was “very good” and was made for man’s enjoyment and utilization (Genesis 1:26-28,31).