Joseph Fielding Smith teaches Flood was the baptism of the earth.
Joseph Fielding Smith, Doctrines of Salvation, comp. Bruce R. McConkie, 3 vols. (Salt Lake City: Bookcraft, 1955), 2:320
Now a word as to the reason for the Flood. It was the baptism of the earth, and that had to be by immersion. If the water did not cover the entire earth, then it was not baptized, for the baptism of the Lord is not pouring or sprinkling. These forms are strictly man made and not part of the gospel ordinances.