The Earth has a lot of water on its surface, in fact, the Earth's surface is about 2/3 covered in water. Interestingly enough, water is not so abundant on any other planet, and scientists have yet to find another planet in our solar system, or anywhere else for that matter, that may have this kind of flowing water on its surface.
The idea that Earth's water was delivered over a long period of time by meteorite delivery may not be too far off from the truth. This gives us an idea of just how old the planet really is, and as a matter of fact, the water delivered would have been delivered very slowly from this process.
On the other hand, the notion is also being challenged because some think that water may have been trapped inside of glass pockets beneath the Earth's surface where it was trapped and slowly made its way to the surface via volcanoes.
The new theory is interesting and puts a new spin on things, which are you more likely to believe?