A bimini extender fits overlappingly onto and extends forward of a pontoon's primary bimini for extended shade. The bimini extender includes a flexible cover that is at least about one-third of the deck surface area of the pontoon boat, a framework configured for attachment to one or both of the deck and pontoon's perimeter railing, a rear attachment structure for attaching the flexible cover to one of the deck, perimeter railing, and primary bimini, and a front attachment structure for attaching the flexible cover to the framework. The flexible cover shades an “extra” portion of the deck surface area. The bimini extender is made to be collapsible, removable, and storable, and further is made with robust and lower-cost components including a novel railing clamp, yet is aesthetic, durable and easily installable/removable.