What does Psalm 24:2 mean?

The point here is not about the exact construction of the planet. Even as stated the meaning is not that the earth rests on water; rather this refers to how God separated the land from the water. He formed the sea and the rivers, the lakes and streams, the springs, ponds, and waterfalls. Genesis 1:2 points out that when God initiated the creation, "the Spirit of God was hovering over the face of the waters."

When civilization reached its lowest moral point, God demonstrated clearly that He owns the waters. He sent a flood to sweep away the entire corrupt human race—with the exception of righteous Noah and his family (Genesis 6—9). The apostle Peter reminds us that "the earth was formed out of water and through water by the word of God [the land appeared from water], and that by means of these the world that then existed was deluged with water and perished" (2 Peter 3:5–6).

The Lord's ownership of the waters is further illustrated by the fact that He caused the flood in Noah's time to abate so that dry land appeared again (Genesis 8:1–5). Such a flood has not recurred, nor will it recur because the Lord promised He would never send such a flood again (Genesis 9:11).