Comet’s water ‘like that of Earth’s oceans’
http://www.freerepublic.com/focus/news/2788555/posts
Solar System Ice: Source of Earth’s Water
http://www.freerepublic.com/focus/chat/2906461/posts
There are planets and moons essentially made of water. So while a comet could be a source, more likely a comet is made of similar stuff to the rest of the space debris.
The universe seems to be made of water and hydrocarbons. Basic building blocks of the universe.