The man who built the ship before the rain
Noah is the second Adam in the Genesis narrative — the figure through whom God begins again after the cataclysm of the flood. "Noah found favor in the eyes of the LORD." (Genesis 6:8) The phrase comes after a sentence that should have ended the story: "every intention of the thoughts of his heart was only evil continually." (Genesis 6:5) The flood is the LORD's response to a creation that has corrupted itself past mending. One household is preserved.
The instructions for the ark are precise and strange. Three hundred cubits long, fifty wide, thirty high. Pitch inside and out. One door. One window near the top. Three decks. The dimensions are given before the rain begins, before Noah has any evidence that what God is saying will happen. The Letter to the Hebrews names this as the structure of Noah's faith: "By faith Noah, being warned by God concerning events as yet unseen, in reverent fear constructed an ark for the saving of his household." (Hebrews 11:7) The ship is built on the word, not on the weather.
The Christian reading of the flood has from the patristic period understood the ark as a typological figure for the church. The water that destroys the world becomes, through the ark, the water that delivers the household. 1 Peter is explicit: "in [the ark] a few, that is, eight persons, were brought safely through water. Baptism, which corresponds to this, now saves you." (1 Peter 3:20–21) The flood is a baptism that judges the old world and births the new. The ark is what carries through.
The sacrifice Noah offers when he disembarks is the hinge of the post-flood covenant. The LORD smells the offering and resolves never again to destroy the earth by water (Genesis 8:21). The rainbow set in the clouds is the sign — a weapon, in ancient Near Eastern imagery, hung up by its archer. The Noahic covenant is universal in scope: with all flesh, every creature, all generations. The Christian reading sees in it the foundation of all subsequent covenants. The Abrahamic narrows to a family. The Mosaic narrows to a nation. The new covenant in Christ widens again to all the nations who come to the Son. Noah's covenant is the floor under all of them.
The figure has a darker postscript. The drunkenness in Genesis 9, the cursing of Canaan, the failure of the new beginning to actually fix what was wrong — these are part of the Genesis honesty. Even the man God preserves through judgment cannot stay righteous. The reader is meant to feel the disappointment. The next eleven chapters spiral toward Babel. The story needs Abraham.