What came first, water or light?

I'm not sure if this will help, but I'll try to be clear.

First, the light Genisis talks about is not physical; it's spiritual. What I mean is, that it wasn't a star that God created, but the light is a symbol. If you read on it says

“And God saw the light, that it was good: and God divided the light from the darkness. And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.”

You'll notice that the Day and Night are capitalized first letters, which could only suggest that they were living things (I'm not so sure how to explain that). The phrase, "...and God divided the light from the darkness..." means that God divided Good and Evil; God and Satan. And, as @Matthew said, God can do anything he likes. He is the God of the Impossible.

I do hope I helped at least the tiniest bit!

Oxygen is produced in stars, and stars give off light, therefore, light existed before water.

Nope. Does not follow. In fact, light existed before stars, which weren't created until Day 4 (Genesis 1:14). You're reading a Materialist belief into the Bible (eisegesis). God made the Universe, and, being all-powerful, is quite capable of making water first.

For me, the "Bible" is the "bible", and it is not the word of God

...well, then, what are you asking? If you reject God's Word, go ask a Materialist which came first.

A definition of the word 'light' is first needed. It seems to be taken for granted that visible light is meant, yet there are myriad forms of light that are not visible to human eyes. Further, at the point in time at which Genesis 1:3 applied, there were no humans around to see anything. Nor were they around when, later, sun, moon and stars were set in the firmament by God so as to give varying degrees of light on to the earth. That kind of light is stated in my Oxford Dictionary to be:

"The natural agent that stimulates the sense of sight; visible electromagnetic radiation from sun, fire, lamp, etc. Medium or condition of space in which this is present and therefore sight is possible (opp. darkness)." (1976 edition, page 627)

Yet the question invokes John chapter 1 which speaks of the Word of God, who was with God in the beginning, and who was God, and who made everything that was made, being light. Indeed,

"In him was life: and the life was the light of men. And the light shineth in the darkness; and the darkness comprehended it not... that all through him might believe... the true Light, which lighteth every man that cometh into the world." (verses 4-9)

The need is to find out whether Genesis 1:3 is speaking about visible, electromagnetic radiation, or some kind of spiritual light emanating from God. Clearly, John chapter 1 is using light in a non-literal sense, for although the Word (Jesus) is "the true Light which lighteth every man that cometh into the world", many humans cannot "see" Jesus in a spiritual, enlightening sense, while many others can.

When you ask if water came before this light, again it is taken as understood that H20 is meant - literal water must be drunk to maintain life in living creatures. And, certainly, the verse in Genesis 1:2 speaks of water and darkness simultaneously being on earth, a division between darkness and night arising when God then commands light to be.

Yet, consider how much the scriptures speak of metaphorical and spiritual waters of life, God being "the fountain of living waters" (Jeremiah 2:13 & 19); the Holy Spirit inviting the Bride to drink of the water of life freely (Revelation 22:17), and Jesus saying the water he gives becomes a spring of water welling up to eternal life (John 4:13-14). All three are involved in this spiritual water and spiritual life, just as all three are involved in literal water and literal light in Genesis.

When questions about the meaning of creation details in Genesis are asked, and there is no clear answer, my answer would simply be to explore the symbolic, spiritual meanings in scripture (of water and light), learning all about those, and then the way Genesis speaks of water and light might become clearer. After all, 1 John 1:5 states that "God is light; in him there is no darkness at all." This means that God is the source of all light so in that sense, God's light has always existed, before any material creation began.