A self-retaining, recessed seal for reception in an open top groove, where the groove is neither configured for seal retention (e.g., convergent side walls), nor provided with seal retention features such as flanges, projections, etc. No adhesives are required, enabling the seal to be easily removed for cleaning, etc. The self-retaining seal has a bottom structure with lateral extensions, wider than the groove, with upwardly angled surfaces at the edges and portions that extend upward when compressed laterally by the walls of the groove. Side walls of the seal extend upward from the bottom structure and are slightly narrower than the groove, to avoid or minimize contact with the groove side walls when the seal is inflated. The configuration enables relatively easy installation of the seal but effectively prevents the seal from “walking” out of the groove over time, with repeated cycles of inflation and deflation.