Yes they are water proof!! :)Idiot... they aren't waterproof. You can go in water with one but i suggest you don't. They will sag stop working as well if they still work at all and they might break...
Because of the algae that grows in the water, as well as fish feces and other impurities that are naturally in water. Also, the fish food contributes to the murkiness of the water, too.
If you mean is water good for you then yes because you can not live without water and besides water is a lot better than soda or juice. Water is a whole lot healthier..