Harmony Kayak Cockpit Cover Extra Large Xl Clearwater The Harmony Clearwater Cockpit Covers are made from a durable, UV resistant 600 denier polyester that won't stretch when wet. The coating is water resistant with enough breath-ability to store boats over time. Not recommended for cartop transport without additional strap to secure to hull. This cover is not watertight. Durable and UV resistant  Material won't stretch when wet