Imagine being a witness to the creation.
The YouTube video below gives you a limited sense of what Genesis 1 describes.
We need to remember that there is no way our puny minds could grasp HOW God created the world.
Moses may have received this as a vision or a dream, and I can imagine him (like John in the book of Revelation) being in the spirit (out of body) observing this poetic vision of God creating the world.