Abstract: A semi-finished composite material for the manufacture of buoyancy products and related products. The semi-finished composite material includes a plurality of layer of elastic and flexible waterproof material with a specific gravity substantially less than that of water, fastening means adaptable for associating the layers to each other so as to form a plurality of air filled spaces by consecutive ones of the fastening means between adjacent layers, wherein the fastening means of a plurality of quiltings spaced from each other so as to form the air filled spaces with the plurality of layers including the air spaces adapted to being further insertable between a lining and a coating.