The Rolex Sea-Dweller line is the result of years of collaboration with experts in the field of deep sea diving. During the 1960s, as the needs of divers evolved, so-called 'ultra-resistant' watches began to be produced. Thanks to their greater crystal thickness, integrated helium escape valves, and thicker case, the Rolex Sea-Dweller models were water resistant at twice the depth of most competitors. Today, watches in the Sea-Dweller line are resistant at depths of up to 4,000 ft (1,220 metres) and retain all of the class and elegance of a Rolex. The high-class design and engineering of the Sea-Dweller are sure to impress, in the deep seas as well as at even the most extravagant of events.