The Rolex Sea-Dweller is one of Rolex's most interesting models. It was first introduced in 1967, after French commercial diving company COMEX approached Rolex with an interesting challenge. Due to growing demand for new oil sources, COMEX was servicing offshore oil and gas rigs that were located at greater and greater ocean depths. As a result, their divers needed to work at these extreme depths for extensive periods of time. This presented the opportunity for Rolex to develop a strong and rugged diving watch to meet these challenges. The model, initially developed from the Submariner, offered such features as increased crystal thickness and depth rating, as well as a helium escape valve and an absence of the date magnifier present on other Rolex models. At Basel World in 2008, Rolex introduced the Sea-Dweller Deep Sea model with a depth rating of 3,900 meters (12,800 ft). This is by far one of the best dive watches in the world, designed for serious, pro divers.