Gaiters keep boots dry if they are built with that intention and have the right fit. The gaiters I featured by Outdoor Research, Kenetrek, and Kahtoola are all made with waterproof materials that are meant to keep your boots dry. Of course, if the toe or sole of your boot isn’t also waterproof, water will come in. Match your waterproof gaiter with a waterproof boot for the best possible protection.