Gen 1:9 ESV – And God said, “Let the waters under the heavens be gathered together into one place, and let the dry land appear.” And it was so.
Gen 1:10 ESV – God called the dry land Earth, and the waters that were gathered together he called Seas. And God saw that it was good.
This has to be a receding of waters that covered the earth. This occurs once more in the flood of Noah, and God promises it wont ever happen again because Yahweh promises never to destroy the living on the Earth by a flood of waters. .
There is an awesome concept called the hydroplate theory which describes what appears scripture is saying. A gathering of waters under an expanse, and then land coming forward and the waters migrating to its own level.
Reading the site about this theory is interesting as it points to land bridges, as well as how the great flood of Noah occurred.
At the very least, what is here is God’s decision that land is what is required for what God wants to do. Although the sea is the majority of the surface of the planet, and the air (atmosphere) is probably the biggest part of the volume, the land is where the focus is, and remains for the rest of the scriptures. Humanity comes forth on the land, but had Yah created man in the air, or the earth, or even in the earth, then the focus would demonstrate that, and then we would see the focus there.
From Earth Fact Sheet
Atmosphere Mass/Volume: 5.15 x 1015 Metric Tons/ 51 x 109 km3
Hydrosphere Mass/Volume: 1.25 X 1018 Metric Tons/1.332 X 109 km3
Land Mass/Volume: ?
Cool picture that seems to relate volumes of water and atmosphere to the planet…