Abstract: Semi-submersible vessels are described comprising one or more modules each comprising a sealed chamber of annular cross-section, a partially immersable support structure secured to the chamber and a platform or deck carried by the support structure. The support structure is preferably comprised by a network of tubular members and preferably the sealed chamber comprises a plurality of toroidal storage reservoirs and ballast tanks. The support structure and chamber can together be in the form of a truncated ovoid narrow end uppermost. In an alternative embodiment the chamber is in the form of an inverted bowl and receives a dome like storage reservoir therein.

Abstract: Semi-submersible vessels are described comprising a sealed chamber with curved surfaces, a partially immersable support structure secured to the chamber and a platform or deck carried by the support structure. Preferably the sealed chamber comprises a plurality of toroidal storage reservoirs and ballast tanks. The lower portion of the vessel formed by the closed chamber opens at its upper portion toward the support structure and at its lower portion through an opening for communication with the liquid of the environment. The vessel additionally comprises a plurality of openings in the proximity of the larger perimeter of the chamber. According to another embodiment, the concavity of the chamber is directed downwardly.

Abstract: A semi-submersible vessel comprising at least one hollow toroidal element adapted to float with its plane upright having an exposed upper portion carrying a working platform. The toroidal element preferably is formed by describing a circular or elliptical locus with the center of a circular or elliptical generating figure, the size of the generating figure being larger at the bottom than at the top of the floating toroidal element.