When experts talk about water, they often speak about the clarity of the water. Clarity is the depth sunlight reaches (usually in the context of an ocean or a stream), and it is of great aesthetic interest. While tiny bubbles in tap water can cause the water to be hazy temporarily, turbidity is cloudiness or haziness caused by light-reflecting particles in the water. It is also the key test of water quality. The less turbidity water has, the more healthful it is. In fact, too much turbidity can lead to gastrointestinal diseases. As we’ve discussed before, “ultra-pure” water can actually be bad for you, but on the opposite end of the scale, too many particles in your water can also be hazardous to your health.