Abstract: A multipurpose floating structure usable as a floating airport or as a floating support for an industrial facility. The structure is made of numerous identical modular units joined in a reticulated pattern. Each modular unit has a removable self-draining deck, groups of removable flotation tanks, a grid framework of beams and girders for holding the tanks and supporting the deck, and a submerged bridging network providing rigid support and stability for the structure. The components are made primarily of waterproofed steel reinforced concrete. The flotation tanks are accessible for purposes of inspection and maintenance, and for adjusting the level of ballast therein.