There appear to be four classifications of all flesh:

1. Fish - creatures that swim in the water.
2. Birds - creatures that fly through the air.
3. Beasts - creatures that are dry-land animals.
4. Creeps - creatures that creep on the earth.

I heard Chuck Swindol say that this method of classification was still in use in Solomon's day.

Genesis 1:20, Genesis 1:24, Genesis 1:26 and Genesis 6:19-20