Although prophecy does say waters/flood refers to people, that is not the case in Noah's flood. It was a literal flood of water.
Assumption. Gen. 2:5, 6 describe a fog that God used to water the earth before any rain. But that was still very early in the creation process. People also assume that people ate only fruit, because God gave them fruit for meat (which just translates to food). I believe God also instructed Adam on which animals he could use for food. We are first given reference to clean creatures in Gen. 7:2 when Noah was gathering animals for the ark. Obviously, that had already been their custom. There were fresh-water rivers then (see Gen. 2:10).
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