Genesis 8:11

And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth.

1. The dove returned that same evening with an olive leaf in her mouth.
2. Noah deduced that the floodwaters were essentially gone. (Since the dove had apparently plucked the leaf off a tree, and since mature olive trees grow 25 to 45 feet high, I wonder why Noah thought the waters were gone - even though olive trees grow in coastal areas.)