Where did water come from?

Scientists are still unsure where all of Earth's water comes from, however there are two major theories:

1. Many comets and asteroids contain water ice, and it is considered that these objects brought a large amount of water to Earth in its early years.

2. Some scientists believe that water came from within the planet itself, maybe hydrogen-oxygen interactions in the early atmosphere and magma oceans.

Both theories offer evidence that these objects may have played a part in delivering water to our planet.

It's worth noting that these are just two possibilities, and there's still a lot we don't know regarding the origins of Earth's water.