@Herald,
As you don't seem to recognize, its a wonderful day when science DOESNT know everything. You can be sure that, what science does know , in order to be sustainable, must be presented in a fashion where evidence is most robust.
The hypotheses of "cometary water" was popular for a number of years but was only "lightly" held as a working hypothesis. When we sent probes to some comets we discovered that the cometarywater had very different ratios of Deuterium to protium in its water (Its like C12 in fossils). However, the ratios of D/P are very similar from Asteroidal water and oceanic water. AND, some of the more exotic off planet elements coincide.
Ive always been a fan of the creation of water on the earth during theLate Hadean and during the Proterozoic (by sulfitic metabolism by chemosynthesizing bacteria, and later by photosynthesis)
{{When H2S is metabolized in the presence of CO2 (all of which are ubiquitous compounds on the early earth) it relases H2O as well as fixing S}} Im not a huge fan of that only because , in the post Hadean, weve had evidence of C12 life in Sea layed sediments and it already showed that water was present in sizeable amounts.
The time when blue green algae developed , I believe that , not only was oxygen freed but additional water was compounded by these new life forms.
THE fossil record supports a gradual increase of oxygen and therefore additional water through time.
(As I said before, I don't have answers to satisfy you, but I can point to EVIENCE that many interacting phenomena , including the advance of life, may have been instrumental in filling up the earths reservoir.
Another hypothesis states that REDOX reactions and differentiation of acidic rocks (such as granites or diorites also added to the water balance (and, as these were first seen in the earths crust, it would mean that the earth was already going through early episodes of continental drift). The evidence for this is pretty straitforward in that all shield rocks show deep time ages and exhibit lots pf quartz rich rocks.
Evidence my dear boy, is that which I prefer to follow. As evidence grows for any one or more of the hypotheses, Ill be satisfied that the answers are closer at hand.
SO what've you got. Any evidence to support it?
As I said before, my work has always been involved looking at the time during which certain vent had occurred on arth. (These events would leave remnants on the presence of economic deposits which folks like me exploit). During ALL of these time sequences from the earliest to most recent, water already existed. So Im in no big hurry to join the water seekers , since the rise of life, during all these intervening "wet eons" has followed Darwins theory damn closely.
Don't see any "Precambrian elephants" in the fossil trove.