Only 3% of the water in our planet is potable. Knowing this, people should treat it as if it was a treasure. But instead of that, they pour hundreds of chemicals into it every day, making it toxic, not just for humans but also for animals, specially fishes.

From my point of view, one of the biggest issues is the excessive amount of toxic materials factories throw into the water, not caring about how harmful that can be.  Because of this, we are starting to see the water of the rivers in big cities is turning black, and losing all the animals that live in it.
However, the water isn't polluted just  because of this. We use a lot of potable water at our houses when it isn't really necessary; for example, when we water our plants, or when we wash the dishes.

In conclusion, we should be careful with the use we give to potable water and try not to pollute it as much as we do. Keep in mind little things can make big changes, so start saving water at home!