7 But what is, “who laid out the earth above the waters”? For it is a difficult question, because the earth seems to be the heavier, so that it should be believed not so much to be borne on the waters, as to bear the waters. And that we may not seem contentiously to maintain our Scriptures against those who think that they have discovered these matters on sure principles, we have a second interpretation to give, that the earth which is inhabited by men, and contains the living creatures of the earth, is “laid out above the waters” because it stands out above the waters which surround it. For when we speak of a city on the sea being built “above the waters,” it is not meant that the sea is under it in the same way as the waters are under the chambers of caverns, or under ships sailing over them; but it is said to be “above” the sea, because it stands up above the sea below it.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)