Historically, how has the fraction of Earth covered by water changed? Today, 70.8% of the Earth is covered in water (± a few tenths of a percent depending on how you account for lakes).1 How has this figure changed over the history of the Earth, and why?

Of course, if we go back to the early Hadean Eon, there were no oceans at all, so obviously there was an upward trend, at least initially - but what was the nature of that upward trend? And, once the oceans were more or less "done" forming, was the fraction of Earth covered by water reasonably constant, or not?
Can't say much about the later epochs, but the 'hellish Hadean' epoch without oceans is kind of an outdated idea.
We have zircon records indicating that crust and oceanic formation was already done to some unknown extent 4.4 Gyrs ago. The zircon analyzed in the nature paper given originates from interaction with sub-crustal material in a watery environment at this date.