Water pollution is caused by many different things that can affect plants, animals and even humans. While we may be making our lawn or crops grow nicely with fertilizer, the fertilizer is polluting our water. Water is polluted also by different forms of sewage, garbage and many other things. Water is the Earth's most precious resource and is home to many animals. Without this resource, life on Earth would be non-existent.

because it dissolves and distributes substances easily

Because it's almost everywhere and we treat it as a dump. Kano is also right about disolving a lot of compounds.

because it has the ability to dissolve a lot of substances.