All Ceatures Great and Small: The Lord God Drowned Them All

You'd think that when God repents, he'd behave better afterwards. But not the God of the Bible; he's at his worst after making a public confession.

Take the flood, for example. God creates all creatures great and small and declares them "very good" in Genesis 1:31. He then makes them not so good in 3:17-18 (either immediately in an evil re-creation or through 1656 years of God-directed super evolution), repents of ever having made them in 6:7, and finally drowns them all in 7:21-23.

What was the point of all that? If God was trying to punish people for misbehaving, then why did he drown the animals, too?