A seal for a window aperture formed in a cover of a dry storage box for viewing a normally handheld portable electronic device therein, and a flexibly resilient membrane substantially filling the window aperture, the membrane including an optically transparent interior portion that is structured for viewing an interior cavity of the box and a continuous peripheral seal surrounding the interior portion and sized to be coupled to the inner peripheral frame of the window aperture; and a clamping mechanism structured for clamping the peripheral seal of the membrane against the inner peripheral frame of the window aperture in a continuous substantially water-resistant relationship therewith.