Atwood Oceanics Inc was organized in 1968 as a Texas corporation and commenced operations in 1970. It is headquartered in Houston, Texas with support offices in Australia, Malaysia, Singapore and the United Kingdom. The Company is an offshore drilling contractor, engaged in drilling and completion of exploratory and developmental oil and gas wells. It owns 13 mobile offshore drilling units located in the U.S. Gulf of Mexico, the Mediterranean Sea, offshore West Africa, offshore Southeast Asia and offshore Australia, is constructing three ultra-deepwater drillships. Its various types of drilling rigs are Ultra-Deep-water Drill-ships, Semisubmersible Rigs, Semisubmersible Tender Assist Rigs and Jack-up Drilling Rigs. The Ultra-Deepwater Drillships are self-propelled vessels, shaped like conventional ships, and are mobile of the major rig types. Semisubmersible rigs have two hulls, the lower of which is capable of being flooded. Semisubmersible tender assist rigs operate similar to semisubmersible rigs except that their drilling equipment is temporarily installed on permanently constructed offshore support platforms. A jack-up drilling rig consists of a single hull supported by at least three legs positioned on the sea floor. It is typically towed to the well site and once on location, its legs are lowered to the sea floor and the unit is raised out of the water by jacking the hull up the legs. It competes with several international offshore drilling contractors. Its competitors include Diamond Offshore Drilling, Inc., Ensco PLC, Noble Corporation, Rowan Companies PLC, Seadrill Limited, and Transocean Ltd. It complies with extensive government regulation in the form of international conventions, federal, state and local laws and regulations in jurisdictions where its vessels operate and are registered. The Company is subject to changing tax laws, treaties and regulations in and between countries in which it operates.