Abstract: A floating platform comprising in combination a semisubmersible vessel (40) having two or more pontoons, buoyant columns upstanding from those pontoons and a deck supported on the columns (the semisubmersible vessel being a kind known per se); and a raft (41) comprising a hull portion and two or more buoyant caissons arranged so that the raft is capable of floating in a stable configuration with the hull portion of the raft submerged to such a depth that the semi submersible vessel (40) can float over the hull portion and with only the buoyant caissons piercing the water surface, in which the pontoons of the semisubmersible vessel (40) are secured to upper surfaces of the hull of the raft (41).