A modular personal flotation system comprising, at least in part, rigid, seamless, non-woven modules, such as a seat module and various pontoon modules, formed by the process of rotational molding or blow molding, from a Linear Low Density Polyethylene (LLDPE), High Density Polyethylene (HDPE), or similar molding resin. The pontoon modules each have a rigid shape, which makes it both unnecessary to inflate and vastly improves the resistance to loss of flotation, creating safer conditions for the user. The pontoon modules are also tolerant of significant relative pressure changes without substantial deformation or change in its shape. Vent hole(s) formed during the molding process are closed to water ingestion via a low-cost bleeder valve assembly. An integral luggage rack can also be molded as part of the center seat module, positioned behind the seat. Open drain holes molded through the seat module double as slots to receive a backpacking harness. The seat module is removably coupled to the pontoon modules by complementary integrally-formed connection interfaces, or by a system of nylon straps with hook and loop fastening sections, eliminating the need for multiple components and fasteners, thus saving weight, complexity, and cost. In an alternative embodiment, a metal frame module may be interposed between oversized pontoon modules and the seat module to configure a flotation system capable of supporting more weight.