If Noah’s flood was worldwide, where did all that water come from and where did it go after the flood?

The waters came from two places. It is possible that there was a water canopy above the earth that God released in the form of rain.

Praise Him, you highest heavens and you waters above the skies.

Psalm 148:4

Most of the water, though, came from under the earth.

In the six hundredth year of Noah’s life, on the seventeenth day of the second month – on that day all the springs of the great deep burst forth and the floodgates of the heavens were opened.

Genesis 7:11

When God created the earth He created the earth covered with water and when He created land, it was set on the waters.

The earth is the Lord’s and everything in it, the world and all who live in it; for He founded it upon the seas and established it upon the waters.

Psalm 24:1-2

It is quite possible that God caused a crack in the earth’s crust allowing water under the crust to come through and cover the earth.

Where did the water go? It is possible that God caused the floor of the oceans to sink allowing the water to flow off the land and into the oceans. You might say… that’s a lot of water to drain in a worldwide flood. And you would be right, but the oceans are very large and very deep.