Earth may have underground 'ocean' three times that on surface

[Anomalocaris]

There are pictures of water coming up from the ocean floor through vents. But I guess some people seem to think that when it rains it's the magic comets delivering their water to Earth.

Ah, no. The water coming out of undersea vents were not made in the earth. They are actually water that was originally already in the oceans, which then seeped into the bedrocks under the sea floor, got heated by volcanic activities near the oceanic spreading enters, and then came out under pressure.

You need to understand earth has multiple hydro cycles that move water between atmosphere, oceans and rivers, and underground. The rain, the springs, the geysers, the hot undersea vents, all just represent preexisting water being moved through hydro cycle. None of it involves newly created water coming out from where they were being made. Earth does not make water. Never did. Ever. Earth has acquired large inventory of water, all were delivered by comets, 99% of it was delivered to earth within the first few hundred million, possibly as few as 1-10 million, years of earth's initial formation 4.6 billion years ago.

Your fixation of "magical impossibility" of amply documented cometary water delivery is getting ridiculous.