of the platform units and these may be readily grasped by personnel using the bridging structure a feature of the invention resides in the fact that a high load or support factor is provided inasmuch as the platform units are supported by their undersides in immediate contact with the surface of the water therefore all loads which are placed on the platform units are distributed over the unit to the surface of the supporting water therebeneath for this reason it is important to note that the inflatable means are at the sides of the platform units so that the platform unit may rest on the surface of the water while the buoyant inflatable means supports the units referring now in detail to fig4 a platform unit such as unit 11 is illustrated wherein the inflatable means 14 on opposite sides of the unit are in their inflated and water supporting position means for inflating the inflation tubes 14 are represented by numeral 30 which is a source of high pressure air having suitable valve means coupled to the interior of the tubes inflation means 30 39 is associated with buoyant inflatable tube 14 39 it can be seen from this figure that the tubes 14 and 14 39 are coupled to the central platform 31 of the unit by flexible straps 32 33 34 and 35 respectively these.