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

[JuliaL]

All water on earth did come from comets, and there is nothing magical about these comets. The comets which brought water to earth are all, as far as we know, normal run of the mill comets.

Is there any consensus opinion on where the water in comets came from?
And why they are so watery rather than rocky?

I ask as someone profoundly astro-geologically ignorant.
.

EDIT:
OK, I'm not too lazy to look at the internet right in front of me.

"Comets are some of the material left over from the formation of the planets. "
"So the Sun is the collapsed core of an interstellar gas cloud, and the planets, asteroids and comets are small lumps of dust or ice chunks which stayed in orbit instead of spiraling into the Sun. "

So I gather that they formed something like giant snowflakes from the atomic hydrogen and oxygen which formed water in a dust and gas cloud.