Water pollution is when water is made dirty or unfit to drink.
One example of water pollution is when you use fertilizers or weed killer on your lawn. When it rains, those chemicals can absorb into the ground and mix with ground water or it could run off into sewers.
Another example is when you pour something down the drain, such as an old carton of milk. When all of everything is cleaned out of the water, sometimes the mess left over is drained into the ocean.
