Question: If the first earth had no sea where did the water come from to cover the earth in the beginning of Genesis? Also, if there were dinosaurs as you believe in the first earth, did they breathe atmosphere and would there have been vegetation for them to consume?
Response: That's a good question. I guess we could also ask where all the water came from during the great flood, enough to "cover the highest mountains to a depth of twenty feet" (Gen.7:19-20) - twenty feet over Mt. Everest world-wide is, I venture to guess, a lot more water than is currently contained in all the world's ice-caps. Or we could ask where it is going to - for in the eternal state "there is no more sea" (Rev.21:1). Or where the water for the massive river that will issue forth from Jerusalem into the Dead Sea will come from (Ezek.47:1-12). The broad answer is clearly that the God who turned water into wine, and who caused water to issue forth from a barren desert rock, enough to quench the thirst of several million people and their livestock (Ex.17:1-7), precisely to prove that "nothing is to hard" for Him, is clearly able to do anything He desires with the material universe. After all, He made all the galaxies, the universe and everything in it, in less than a blink of an eye - He can surely produce as much water as He wants, whether it comes from something or from nothing. We do know that His production of much of this water about which you ask came prior to His rehabilitation of earth, because in its "lock-down" state, earth was covered entirely by waters (Gen.1:1-2), so that another question might be, where did all that excess water go when He separated water from dry land? Truly, nothing is impossible for our God. As to the conditions on the primeval earth, again, I can only speculate. It seems clear from what we have in the "fossil record" that all these creatures were constructed along the lines of today's fauna (they had analogous systems, lungs or gills, etc.), and the remains of plant life are also similar in construction (even the fossilized pollen is similar, I believe), with the result that archaeologists posit a very similar world, and perhaps not unreasonably so. But their picture is, of course, not informed by knowledge of what earth was (as the seat of the original Eden and place of God, it must have far more beautiful than earth is today) or of what caused the catastrophic change (the devil's rebellion - see the Satanic Rebellion series).
For more on all this, please see the following links:
The Waters Above
The Waters Above the Heaven
The Seven Days of Re-Creation
Yours in Christ,