Yes, it is very good to drink more water. Generally speaking, you should drink between 8 and 10 glasses of water each day. And as your mom has said, drinking water can do a good job to your eyes. For example, by drinking water, it makes your eyes and mouth moist. It washes dirt and dust right from your eyes. And in this way, it can decrease the risk you get the dry eyes. On the other hand, you should know that, water is not only good for your eyes, but also for your other parts of your body, such as the brain, the cells, and the organs. For example, Drinking water is like oiling your body's joints. Water lubricates the joints, keeping them versatile, and ensuring seamless motion. Anyway, just drink more water.