Some think that the water of Earth and the planets came from a comet impact in the past
Such idea that water came to our Earth from a comet is extremely imaginative and not realistic
Their mistake comes from an erroneous presumption that the comet is a dirty ice

The origin of water of Earth and the planets

Water of Earth (and the planets) came from the earth (and the planet) itself, as is the atmosphere

The explanation
Earth was a fire object at the start, because it was part of an exploded sun. From every fire object, gases and smoke emerge; the smoke was a mixture of seven gases; among these gases was the O2 and H2, then by electric current the H2O resulted