There is no Canaanite pagan mythology involved. All false religions worship the creation of "mother earth", only in Christianity is there a Creator. Water was already there because it was a part of the earth created in 1:1. Later in Noah's Flood it was mentioned that water came from "fountains of the deep". Till this day the main source of fresh drinking water is still underground water.
That’s why genesis 1 mentions the tannin in genesis 1.
https://biblehub.com/hebrew/8577.htm
It’s paralleling the separation of the waters with the separation of the sea dragon as brought to light in psalms 74.
Psalm 74:12-17
New American Standard Bible
12 Yet God is my King from long ago,
Who performs acts of salvation in the midst of the earth.
13 You divided the sea by Your strength;
You broke the heads of the sea monsters in the waters.
14 You crushed the heads of Leviathan;
You gave him as food for the creatures of the wilderness.
15 You broke open springs and torrents;
You dried up ever-flowing streams.
16 Yours is the day, Yours also is the night;
You have prepared the light and the sun.
17 You have established all the boundaries of the earth;
You have created summer and winter.
The Tanakh, or epistles, are not concordistic in nature. They seem to be an accommodation to ancient people. Yahweh spoke to ancient Jewish people in a way that they could understand by drawing upon their Mesopotamian culture and heritage which included the Canaanite mythos and in general the steppes of Central Asia and Middle East.
This link talks a bit about it.
https://www.haaretz.com/amp/jewish/.premium-where-did-creation-story-come-from-1.5404560
All of this is why revelation mentions no sea in the second restoration of heaven and earth ( new heaven and earth ).
Revelation 21:1
New American Standard Bible
The New Heaven and Earth
21 Then I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea.