Abstract: A pontoon float has a flexible collapsible structure which may be extended by interlinking pontoon float platforms to form an elongated platform as for a dock or pier. Each pontoon float platform is supported by a rectilinear array of removable, stackable hollow floats, removably fastened to permanently affixed lid sections, forming an air tight seal. The individual floats are secured to the platform only by removable upper ends, and are otherwise free. The floats may be readily removed and stacked, reducing each pontoon platform to a planar section and a stacked, compact array of float members. The pontoon sections are reinforced by a grid of stringers, providing adequate rigidity without undue stiffness. Preferably, each pontoon sections is provided with interlocking extension plates on an end and a side and a mating pattern of interlocking holes on a second end and side so that they can be adjoined to form complex large floating structures as required.