Dear unknown and 6days,
'Let the earth bring forth' (the vegetation He created) the grass and plants, and trees means that they will be dirt(earth)-based life with the seed within itself (in it's fruit or pod), whereas 'Let the waters bring forth' life, means the creatures that are water-based (and God created whales, porpoises, sharks, manta rays, and fish, etc.) and fowl (ducks, geese, swans, loons, seagulls, pelicans, and sky flying birds also), etc. It is just the way God wanted to express Himself whether things were created from the waters or the dirt/dust of the ground. Likewise, God created the animals and man from the ground and water. Man is what, 75% water? God is a great chemist, of course. Would you expect anything less?
In His Love,
Michael