In the Ancient Near East (I'll call it ANE), there are some standard forms used to explain the origin of the cosmos, whether it’s Babylonian, Ugaritic, or the older Sumerian writings. Israel, too, joins this crowd as Genesis 1 has much in common especially with the Babylonian text Enuma Elish. Genesis 1 speaks in the same categories, answers the same questions, and ‘breathes the same air’ as Enuma Elish (or the other ANE cosmologies). Genesis 1 is firmly settled in its ancient context—with strong similarities as well as sharp differences. I think both are important.
How does Genesis 1 compare? The similarities and the differences of the watery chaos are striking. First, the water is still present in Israel's creation story. It's called "the deep" (Gen 1:2), or tehom in Hebrew (which many scholars say is linguistically connected to Tiamat). The waters are even there before Day 1. But notice that the water is not threatening, as they were with Tiamat! There are no chaotic sea monsters to defeat (in Gen 1 at least; cf. Psalm 74:13), in fact he creates them, too (Gen 1:21)! The difference is as striking as the similarity with the other stories—there is no struggle to conquer the deep, or even to tame it; the spirit of God hovers over it. YHWH has no rival!
Second, prior to creation the world is in a state of disorder. YHWH has no enemy to defeat, but there is still chaos needing function. The cosmos is tohubohu--chaotic--tohu means formless and bohu means empty. So, how does YHWH establish his reign over the chaos? Again, He acts effortlessly; with only a word He creates from chaos. He orders the cosmos on Days 1-3. He takes what was tohu (formless) and gives it structure. Then he takes those empty (bohu) structures, and on Days 4-6 He fills them with creatures. On Day 7 God rests. Step by step, in a concise presentation, YHWH establishes light, divides the waters, forms the land, establishes the luminaries, fills creation, creates mankind, and then rests in His temple. YHWH makes the cosmos his home. That last part should give you pause because it often goes unseen, unless you're looking with ancient eyes. As Prof. John Walton says, any ancient reader would recognize YHWH entering his temple to rest--which is important because they considered the temple the control center for the cosmos.
This helps us see the purpose behind the creation stories in Israel's ancient world. Think of it like this: when you take a new job, are you more concerned with who you report to and where his/her office is, or are you asking instead about the company's ribbon cutting ceremony and its historical development? Israel, too, answered more about "who/why?" in creation, than "what?". They wanted to know who was in charge, not when/how it was founded, as many modern Christians ask of Genesis. Genesis speaks in its ancient context, not ours.
Put another way, the ANE stories (Genesis included) deal with functions, not materials. Much like the new construction project on my new house--I'm describing the work of making a house our home. I'm giving order, purpose, and function to a big mess (though mine's not watery), and then I'm filling and decorating it (I use "I" here loosely. Read: Kelsey).
There are many other similarities and differences from other ANE cosmologies, but the point is clear: YHWH alone is God. In context, Genesis 1 is a not-so-subtle critique of the theology and worldview of Israel's neighbors. More still, it's a unique declaration of Israel's God, YHWH, and His sovereignty and creative power. Amazingly, the Israelites who were coming out of Babylonian exile still had the faith to declare that their God alone was Creator. YHWH is not threatened, is never rivaled. He creates effortlessly, beautifully, and powerfully with only His Word. Praise be to the One true God!