A swimming pool having sidewalls constructed from a series of prefabricated modular panels connected at the ends to enclose the interior of the pool. The panels are preferably formed of foamed synthetic resinous composition and of a limited number of configurations or modules which are interchangeably adapted for use in forming pools having a plurality of shapes, e.g. a straight panel, a concave curved panel and a convex curved panel. Each panel is adapted to mate and lock with the adjoining panel, and with an upper and with flanges and rib arrangements which are functional as well as serve to strengthen the panel. In a specific embodiment, a tongue is formed on the flange on one side and a mating groove on the flange on the other side of each panel for instant connecting and interlocking of adjacent panels when they are assembled in forming the pool wall. A sealing strip may be placed within the groove and abuts on the tongue of the adjoining panel thereby precluding leakage between the panels. Support is provided for each panel by at least one brace, preferably molded from synthetic resinous composition, which is positioned to extend normal to or radially from the panel. The brace in a preferred embodiment is formed so that it functions also to interlock adjoining panels by means of clamping means formed at the extremities of the brace. The clamping elements secure and lock two adjacent panels at their juncture. The swimming pool wall modules and brace are arranged to accommodate a pool deck also preferably formed of molded plastic modules. Each deck module may comprise a tongue and groove interlock structure similar to that of the wall panels. The inner periphery of the deck is adapted to be supported on wall panels preferably on an integrally formed flange of the wall panel. The deck is arranged, in a preferred embodiment, to be interlocked into a unitary structure with the wall modules by means of braces which are adapted to clamp the depending flanges or extensions of two adjoining deck modules as well as those of two adjoining wall modules. A coping may be attached to the top edge of the panels and may comprise an extension of the deck surrounding the periphery of the pool. The coping includes means for optionally attaching a plastic pool liner. As an alternative embodiment a wall panel module may be formed with a horizontally extending slot in the inner wall adjacent the bottom edge of the modular side panels for receiving and securing a bead of a plastic liner adapted to cover essentially only the bottom (rather than the sidewall also) of the pool. A bow string clamp, pressed into the slot upon the bead secures the liner in place enhancing water tight integrity. The intermediate rib structure of the panel module is in a preferred embodiment designed to allow nesting therein of the brace when the wall panels are shipped. A modular wall panel may incorporate ladder steps facing the inside of the pool which is adapted also to receive a handrail.