Abstract: The invention is a kayak cockpit cover which is complementary to a channel formed in the kayak deck at the cockpit perimeter. The cover has a conventional closure around the kayak paddler's waist and a planar covering section spanning the cockpit opening. An edge assembly at the outer margin of the covering section includes a doubled section of fabric forming an endless sleeve around the cover, an endless resilient inflatable tube carried inside the sleeve, and a valve integral with the tube. A core element within the inflatable tube aids in manipulation of the edge assembly and fixes its length. When the edge assembly is inserted into the channel around the cockpit perimeter and the resilient tube is inflated, a watertight seal is formed as the expansion of the tube presses the skirt edge fabric against the channel interior wall, while the bulk of the inflated tube secures the cover edge to the kayak deck.