What is waterproof zipper for?

Do you have any experiences that water still leaked into your bags or shoes even the cover is waterproof?

The zipper may be the pain in the neck because it's not waterproof.
For ease the pressure brought by lives, today more and more people become field sports enthusiast. Water activities are therefore frequent as well. This makes water-repellent products hot, such as clothing, footwear, tents, and other motorbike-use articles. However, these products might be useless because of their pervasive zippers. Your personal valuable stuff might still have chances to get wet and even malfunctioned. So before buying waterproof commodities, be sure if the zipper is waterproof.