toroidal body of revolution in the form of an annular storage tank or chamber having a vertical axis the storage chamber consists of a dish shaped bottom plate 2 preferably curved in a semi elliptical form and of a top plate of a somewhat flatter curved construction the bottom plate 2 has a concave upwardly facing surface while the top plate 3 has a concave downwardly facing surface the radially inner and outer edges of the plates are connected to one another the central opening provided by the annular chamber is covered by a closure member 4 radial fins 5 extending radially outwardly from the vertical axis of the chamber to the crown of the top plate 3 serve as reinforcement and if necessary as a support for a planar top surface not shown if the float construction is used as a platform for a drilling island for the construction of a liquefying plant the outer circumference of the float construction that is the outer peripheral edge of the storage chamber is surrounded by a vertically extending cylindrical wall 6 which extends both above and below the surface of the body of water on which the float member rests below the downwardly facing surface of the lower plate 2 radial partitions 7 extend inwardly from the cylindrical.